Just click on the donut to earn them, and use the hand to give you a donut boost it costs 50 donuts. When you have enough to buy a building just click on it. If yo have more donuts than the world high-score click on the save icon and the high-score will change to your score
Thanks to @45680 for the hand sprite! I have got most of the sprites from google or the scratch libary. (More buildings on the way)