I wanted to have a go at making a few adjustments to the starting 11 according to formation on the override section. So for instance move my slb that isn't used into one if the plays and another time swap two players. Also include my te as a WR to test that. .....

But how do you do it? ! When I click a player square it just turns red and nothing happens!

I'm sure it's something obvious hence the thread title!

Drag a player from the section on top to one of the positions in the override diagram. That position will turn red and show the name of the player you put there.