How do I make an enemy targeting system for a turn based rpg?

Note:I'm new to Construct 3,so I probably can't handle extremely complex solutions.Right now I just want to know the type of logic it would require to do this.

Your question is too big. I would start by puting 3 sprites on the screen, one called friend1 and enemy1,enemy2. If you click on an enemy flash the enemy if you click on a friend do nothing.

If you get that far you have made a start.

Thanks for the idea. I was trying to make it a square outlining enemies to target them,but seeing I'm new,I should probably go with the simpler way of making a rpg comba system that you suggested.