It's pretty easy you just write it in word document programs like Notepad. I use microsoft word because it has spell check, Once you've finished a chapter besure to proof read it for any spelling and/or possible grammar errors. Here's a link to my stories:
"All of Us"
"We're back!" (the sequel)
I can send you links to the profiles of other users from this forum who are also writers on this site. I'll explain later onhow to write and post fan fiction on the site.