Assuming no one has replied to you about it. Get your team first, if you don't know what you can use and can't use I suggest you go to /warp gyms and find the board that tells you all about gyms and what is allowed in gym fights. After that type /gyms to check whats available and what the level cap of a certain gym type is. After that you should be set to applying for gym leader, don't worry if you don't get accepted the first time. Its always common, read the advice they give you about your team and try to adjust to that. In the fortunate event you do get accepted, be ready to build a gym towards your gym type. It doesn't have to be super huge, but at least make it related to the type you're applying for.
I could help guide you thru the process, but (atleast to my knowledge) gym leaders currently aren't a thing, 'cause reset and what not, you could still apply in theory, but you most likely wouldn't get your team, because if I'm not mistaken they're adjusting the plugin right now.