Always type in the app's name, repository and your nickname (right at the end)
If the app has an app id, please fill it (so that the file will be correctly named)
If the app provides Appstream Metadata (.xml file with appdata or metainfo in its file name, often in the project root or /data folder), make sure to link the raw text only variant of it in AppStream XML URL (raw)
If that's not the case, make sure to fill all mandatory fields (marked with M)
Hit save, and you have a prefilled file. If you have filled the repology flathub, or appstream fields, you can now augment the listing by running the checkers - see the checkers README for details.
Then submit the file via GitLab or E-Mail (and if that's too complicated, just uploading it into the Matrix room is also fine!) - Thank you!
Fields marked with M are mandatory, fields with R should be filled if possible, fields with A can be filled automatically afterwards.