How do you upload maps!

Simple question: How can I upload my maps to https://www.doomworld.com/idgames/

Thank you!

You don't.

You upload them to the /idgames archive, which isn't on Doomworld in fact. They will then appear on Doomworld's idgames interface(s) once they have been accepted into the /idgames archive.

You can find some instructions here (start at point 6 or 7). Or you could read the archive's own instructions, which can be found here.