The sauna isn’t quite what you imagine. Most guys are very respectful of you decline their advances a simple “no thanks” will do.
Pretty much you can do as much as you want to either in private or public, I’d suggest you go and have a look around see how things go down relax in the sauna or hot tub and when your ready if you see someone who catches your go have some fun. Mist things start with eye contact, but just be aware if your openly wanking in the cinema room guys may try and suck you off and in the dark rooms people will probably touch you up as you pass by.
Hope you have fun