So, I'm a total Arma noob, literally just bought the game today, entirely because I've watched a certain streamer playing Antistasi and it looks amazing. So far it's really cool, but I have an issue, I don't know how to interact with the base flag, the map or Petros. Which means I can't save, I can't access certain game options (I think that's what the flag does?) and I can't request missions from our big bad boss Petros.

I don't think it's a bug, I think I'm just stupid and am missing something obvious, maybe I just don't know the right button to push (Is it space like when I open the garage and armory?). Either way I would like to request help.