How early do I have to get to NRG stadium for tomorrow’s Copa America game?

I have never went to a sports event so I am not sure how early I have to get there? The game starts at 8PM. I plan on parking at 1000 Fanin St and taking an Uber or Metro to NRG Stadium.

I have never taken a metro rail- do I just hop on the rail and pay after or is there an advanced payment thru an app?

Thanks