Quit grabbing at my tits!
It's fine if you didn't read the last page, but read this one.
Click (or tap) the stash on the right or a tower (stack) you control, then click to place.
Green goes first.
There's a turn indicator near the bottom which changes colour.
Right-click rotates a piece, or you can use the huge button at the bottom if it's on-screen.
REMEMBER: First turn you place an opponent's piece, and it must be flat.