Greetings, this post should be on Support but I'm going to answer anyway. Anyone can upload chapters: if you never uploaded any, the first one you do per language will require approval from the mods, which consists in waiting a bit before seeing it uploaded. After that first step, the chapters you upload will be automatically approved. Returning to your question, you don't need to be part of any group: as long as the group is not restricted to the member of said group, anyone can add chapters under their name. Read all the guidelines of course (if your chapters never appeared it may be because you didn't credit properly the groups), essentially you need to upload the chapters without removing anything (except the links that were mentioned in the post dedicated to that site) and using the name of the group that did the scanlation, you can't upload them under No Group since they belong to a specific scanlation group. In case you need to create new title pages, check
this tutorial and check the rest of the
Tutorial subforum. In case you want to be a scanlator yourself, you can upload chapters using the option of No Group, you simply need to tick the box.