You will learn on the “job” mostly, but the main things:

Be decisive, indecisiveness will lead to your team getting killed. Use decisive language too. “We push, we move here, we stay here” not “I think, maybe, perhaps” etc. You do or you don’t

Your team needs to know what you want to do. With one guy I play with he knows generally speaking what I want to do, but another does not. That means I generally think out loud. Try to make them understand the bigger picture. When I say we need to push/fight this team, I’ll already have said WHY i think that they should be pushed or fought. Or not fight them.

Lead but also listen. One of my friends gets panicky and tends to play passive by default. When he gets insecure about a fight or position I say “no we’re fine” if we are fine. You need to think of it as a veto. He wants to leave, I veto and say no. However, in some situations an opportunity arises I did not notice, so I listen. If my team pushes by their own, I follow regardless.

All in all you need good gamesense and good situational awareness. Most of that you learn as you play.

Don’t worry, you’ll fuck up when you make a decision. Just make a decision , follow rule 1