For food: Click on it. Then drag mouse over dog and wait for it to go back to the main screen. For water: Click on water. Then drag your mouse over the dog until it switches back to the main screen. For exercise: Click on the leash. Then click the leash until the dog is over it. Then wait until the screen switches back.
It doesn't matter what you name the dog. Also, the timer in the top left doesn't mean anything. Next may be coming out soon...
