Lemmy.ml currently (and probably for the forseeable future) doesn't allow the creation of new communities. You could ask the admin to create a community for you, but I can't say more beyond that. I don't know if that's okay or not, I don't have an account on lemmy.ml.
Another alternative is to create an account on another instances that allow new communities and create a community there.
I don't think contacting the admins is likely to help. I don't have the link handy, but the lemmy.ml admins recently posted about turning off community creation, and the general vibe was that as the founding instance of the threadiverse, lemmy.ml holds an unhealthy fraction of its communities. They're going to correct this by letting the rest of the instances catch up by hosting newly created communities.
So there would have to be a real good reason to host specifically on lemmy.ml, and there aren't very many such reasons that a non-admin would have.