Just started playing on PS5, I have a newbie question.

I'm a totally new player lacking video-game skills, (I guess I don't play a lot of fps type games.)

I have what is possibly a dumb question about the very first mission, (I mean the one right after the training session, where you go with Jackie to enter an apartment to fight with some baddies and capture/kill (?) someone.

I saw a message flash up at the start about mounting a grenade. I went into the inventory and thought I had it mounted, but then in action I had no idea how to use it, or even if it was activated.

I didn't last long, I even totally forgot to press the top button on the left hand side of the controller to use health restore, but it was clear grenades were needed in the fight.

Can someone give a quick rundown on weapon mounting and use for a newb? PS5 related?