Although the user page itself is an out-of-universe page describing you (with however little or much detail you're comfortable) and your work, you may post any Star Wars-related fanon on the mainspace, as long as it complies with the site policies. To create a new fanon page, just mouse over the three vertical dots in the upper right of any page and click "Add new page" from the dropdown menu. If you'd like a little extra help, mousing over "Getting Started" in the top menu will show "Create a..." prompts for common topics, and you can check out the community-voted best articles here for guidance and inspiration.