Be mildly competent at computers... or know someone who is and willing to help you.

Either setup your own instance, or find an instance that's already setup that you like and the owner will let you add stuff to the database...

Start a community...

Read here... https://github.com/rileynull/RedditLemmyImporter

Success! now you've migrated your subreddit to lemmy!

(This is a little sarcastic. I'm not good at legit guides. But it is possible!)

Edit: tweaked phrasing... doing this to general public servers would be unlikely.