TLDR: Is there a way I can just choose files to seed automatically instead of downloading again first?

Pretty new to using torrents and I have a bunch of files I’ve been able to download over time through magnet links. Some of which I was unable to seed for long periods of time so removed but would like to be able to still seed them again.

It doesn’t look like I have torrent files for them and I tried copying the. Torrent file to another folder when using magnets to see if I could get it from that. I was able to get some from that but it seems to just start a Download again. Can anyone explain this process a little bit better for me so I can offer up my files at later times too?