You can make an article for your character on our fanon portal by going to this page and using the fourth box - create a fanon character - and build your article from there. Just make sure your article meets our standards and the image is sourced properly, which you can do with an imagebox.
Feel free to ask if you have any further questions.
If you're unable to finish, you can copy/paste your article into a sandbox page for yourself, which you can do by adding "/sandbox" to your userpage link - for example: User:Lilspongelisa/Sandbox. You can also click on that link and create the article from there. Note though that your image would have to be deleted for the time being (admins can restore it) as uploaded images must be used in an article somewhere.
I did note the basics, but again, feel free to ask any further questions if you have them.