How to get people come to your community: instance agnostic links for federation
If you created a sub, by default not a single person get notified about it: it can only be seen in the communities list of your instance. But don't worry it's pretty easy to change it
How to get people see your community
Write good description of what it is about, what is going to be posted, what's to be expected
Craft instance agnostic link to it. Replace "!sub-name@instance" for yours in this link (see the footnote for Lemmy 0.18+)[^1] [Search to federate this sub to your instance](/search/q/!sub-name@instance/type/All/sort/TopAll/listing_type/All/community_id/0/creator_id/0/page/1). It will direct people to search for your community on their own instance.
Post it to meta/main community of your instance: for example !meta@sopuli.xyz
That's it, by reposting it just twice you dramatically increase discoverability of your community. Of course you may find additional community-promo subs but posting in at least these basic two is a good start
Good luck!
[^1]: Lemmy 0.18.0. [This link will fetch CommunityName to your instance](/search?q=!communityname%40instance&type=Communities&listingType=All&page=1&sort=TopAll)
Change communityname with community name, and instance with instance link (without https://)