Look at the bar right below the banner.
*Click "Articles"
*Click "write article" on the right hand side of the blue title bar

The rest should be self explanatory, but if not:
*Type or past your fanfiction
*Add a title
*Select "fan fiction" as your article type from the drop menu
*Add a description
*Add keywords
*You can preview if you want
*Click "publish"

awwww thankz. ;)