Not sure what I can add here that hasn't already been said. This story suffers from erratic pace, contrived plot devices, lacks atmosphere and build-up, lacks conflict or character development and switches between reading like a Wikipedia article to a story very quickly.
I'll give you a few quick examples:
PACE/TEMPO/CONTINUITY: The story struggles to maintain its own logic. The character knows its the Red Man during the encounter but then has to go and research to find out that it's the Red Man. I understand that he's telling a story from the past and at the time of telling would know from the research he did, but you have to remember that the reader is moving at the same speed as the words appear. In order to bring the reader into the story and create that fear factor, they have to see things as the character sees them at the time.
CONTRIVED WRITING: If this were written in 3rd person it would seem a bit less forced. But for a 1st person story, everything shouldn't be falling so neatly where it needs to be in order to advance the plot. Real life doesn't happen that way and with 1st person stories you're kind of doing things in real time because you can't rely on prose to fill in the blanks. The guy gets a necklace that somehow ties in, guy just happens to be walking in the right place for this thing to appear, guy happens to find all the information. Now, obviously all of these things have to happen in order to make the story go, but for something this short there are simply too many moving pieces for it to seem natural at all.
ATMOSPHERE: Once again a result of the story being rushed. There needs to be some degree of descriptive writing here so the reader can develop some immersion into what's going on. Plus the character identifies the Red Man immediately which takes all the elements of "who is the creepy man standing on the corner watching me," out of the story.
NO CONFLICT: The Red Man shows up and the guy runs to safety. Where was the hiding, where was the stalking, where was the ominous sensation of being watched? The character reacts to the Red Man the same way someone would react to a mountain lion. Sure, the idea of a mountain lion chasing you is terrifying, but it's not really horrifying. There is no mental or emotional turmoil, just a fight or flight reaction.
REVERSE WRITING: Reading this I get the idea that it is designed to be a vessel for the Red Man instead of a story about a guy encountering some sort of unexplainable entity. If you want to write a story about the Red Man, write it from his point of view. Maybe write a story about a police officer trying to track down what they think is a killer masquerading as an urban legend, only to learn at the end that it isn't a masquerade at all. This is far too short though to properly introduce a protagonist that the reader will care about and an antagonist that the reader will fear.
CONCLUSION: First off, and I say this with any negative critiques that I have to give, you get kudos from me for wanting to write. Keep going with it and develop your skills.
I'm sure that if I could go back in time to the early 90's when I was writing Mortal Kombat fanficiton in a spiral notebook at school, those stories would probably make me laugh or cry, but either way I know they weren't good. (I literally wrote a story where Liu Kang went to outer space to fight evil. He punches an astronaut, steals his helmet and somehow boards a rocket without the other astronauts realizing he's not the guy that's supposed to be there.) But I'm glad I wrote those and I am glad that I grew and improved.
With that said, this story, in my opinion at least, is not going to work out no matter what you do with it. Can you still make a story about the Red Man? Sure I guess. But based on this draft that you've posted here, it would be easier to start from scratch than try and edit around this. Almost every aspect needs to be edited to some extent, and I think you'd find it a lot easier to just start over with a fresh canvas.
I'd suggest, based on the level of experience displayed in this story, that you go and hone your craft a bit more on sites with looser quality standards. Deviantart or Wattpad are two suggestions. Write and get feedback. Write and Google some basic rules of story composition. Write and read. Keep writing, keep sharing and keep growing. There is no secret sauce to getting great at writing, but there are a few steps to get better.
First, take your time. Writing is an art just like painting, sculpture, music, etc. If you rush through it because you want to see it posted on a horror site, you're missing the point of writing. There is no immediate gratification. There is only a brutal learning curve and lots of readers out there that are a whole hell of a lot harsher than anyone here has been. I've had my work roasted to hell and back, it sucks, but it happens.
Read the advice. Everything that I've posted here and those above me are opinions based off of reading this story as I'd read any other story already posted. Don't debate what we point out as flaws, because if you have to explain something to the reader from the author's point of view, that means that you didn't accomplish the goal of storytelling, because the characters should be explaining things, not the writer. You're certainly not required to follow any of the advice, hence why I started this by saying "read the advice" instead of "take the advice." My opinions and suggestions are based largely on how I would do things and may not match your style. Either way, if you desire to become a better writer and not have to worry about quality standards getting in your way, you'll need to sharpen your methods up.
Finally, go and discover your writer voice. This story is cliche. It's essentially an OC Creepypasta. There are about a million out there that follow this exact formula. I fully understand that all writing is formulaic to an extent. It has to be in order to convey a plot line. But I feel like if you replaced the Red Man with any other generic OC, you'd get the exact same story but with a different title.
I hope this advice helps you and I encourage you to remain motivated and keep creating. Rome wasn't built in a day as they say. Adjust your horizons and stop writing to reach the end. Write to tell the story and only let the natural creative process determine the end. Best of luck to you. Feel free to reach out if I can be of any further assistance.