You need to get at least one user on another instance to sub to your community manually. Before you do that, you will only be discoverable by users on the local instance. Once you get that first user, posts in your community will start appearing in "all" on that other instance.
After you get a sub from some other instance, regular posting will help users find you by just seeing posts from your community on their instance, and they can easily click the community name and sub to it.
Aside from this fediverse-specific quirk, @thegiddystitcher@lemm.ee already posted some good tips.