You can say both:
Die Männer sind hier. (The men are here.)
Sie sind hier. (They are here.)
Hope that's what you mean...
It's the same as in English. So if you're referring to specific men you can use "they/sie", but if you're talking about men in general, you'd of course say "Men/Männer".
Edit: and yes, if it's multiple men, then you conjugate it as "they".