To answer your questions:
1: You can put your story in the writer's workshop at any time. Just be sure to follow our forum rules and be aware that revised stories need to pass an appeal or be given the all-clear by an admin before they can be re-uploaded. Re-uploading without that permission will result in the work being deleted again.
2: The guidelines I gave should give an idea of how the workshop functions. You go to the writer's workshop (link on your talk page if you're having difficulties finding it), go to start a discussion and put in the title, after that you post the story into the text box below labeled 'post a new message to the writer's workshop board' with any concerns or information you want to add. Typically it may take a couple of days to a week to get feedback depending on the reviewers.
3: What I wrote for #2 gives the step-by-step process for posting to the writer's workshop. Here's a pastebin of your story if you don't have a copy. Additionally, I would suggest reading over what I posted on your talk page for a more in-depth explanation of the issues I found in your story/poem as you're revising and before making an appeal. Best of luck.