Ok, I created a torrent file, then uploaded and filled everything to the Upload page.
Then I re-download the recently uploaded torrent file and launch it to start seeding. But the torrent program (Folx) doesn't start checking the folder with files to start seeding.
What's the problem? Could you help me please??

So, there are 2 options:

1. The torrent client ALREADY HAS the torrent (some do that when they CREATE the torrent. Because it was already there, and because it's a "private" torrent, the trackers aren't "merged" so only the original (useless) one remains.
   TO FIX: Delete the torrent (being CAREFUL to NOT DELETE the DATA!) in your client, then re-download from the site

2. The torrent client does not see the files that makeup the torrent in your default download location... you need to tell the torrent client WHERE the file(s) already exist. Otherwise, it thinks this is a new download.
   TO FIX: Delete the torrent (being CAREFUL to NOT DELETE the DATA!) in your client, then re-download from the site - and point your client to the RIGHT location of where you file(s) actually exist!