Emma, to join ILLUMINATION, you need to first, fill in a simple form that you will find if you scroll through this document:
illumination/submission-guidelines
Once they have accepted you, that publication will be automatically to your list of publications (or become the first one there).
Then, when you have a draft article ready to publish, you can use the three dots at top-right of your draft to get the drop-down menu that has an item called 'add to a publication' ... then follow the prompts.
It sounds complicated, but just start off and see how you go ... let me know if you 'get stuck' and I will do my best to help.
Fred
👍😊❤