Writing a catchy sidebar and finding masthead images for your community are the hardest part. Read the Lemmy help doc about markdown formatting and familiarize yourself with it.

When you finally create your community and settle on a name that isn’t taken on this instance, or any other, make posts that advertise you are looking for moderators, graphic designers, et al, and use the sticky post option.

When you find and vet potential mods for your community, make chat group off-site so you can discuss your community moderation in real-time. Discord or Element would be my recommendations.

As for promoting your community, there are communities that specifically cater to stuff like that where you can freely advertise your new community. Your first stop should posting in New Communities.

Another thing that helped me was reaching out to moderators of other communities that I liked and asking if they wanted to “parter” with mine. Basically what partnering is you throw up a link to their’s in your sidebar and they do the same for you.

Hope this helps. It’s not as confusing as it sounds. Good luck!