I can't upload PK3 files

Every time I try to put my mod in submissions, it says this:

You must upload at least one attachment to submit this entry. If you are submitting an addon, it may be necessary to split the music into a separate WAD file to enable you to upload it within out attachment limits. Click here to return to the previous page.

how do I fix this?

Make sure you're uploading some screenshots to accompany your file.

Alternatively, if it is giving you an error when uploading the PK3 file, try adding it to a zip file then upload that.

okie dokie, and thank you again.