This is a turn based game. Here is how I would start.
both players on screen. Controls for player 1 on screen, on tapping any of the controls, they disappear (so no more action buttons can be pushed).
Then you make all the animation (damage and things) happen to player 2.
Then you have a variable switch to 2 (switches between 1 and 2), then because it's at 2, player 2's controls would appear on screen.
Once he takes his turn, it would just swap back to player 1. Back and forth until one dies.
PLEASE NOTE: I see you are fairly new to Construct. I would recommend something a bit more on the easier side of things to start.
If you need any more help, just ask!