Use the arrow keys to move, use wasd to select the direction you mine in, 'm' to mine, and 'b' to place a bomb. you need to buy keys to go deeper underground, and you can upgrade your pickaxe by clicking on the houses scattered around the map. Some houses will let you right click on them, and they will let you buy other stuff. You have a base inventory size of 10, and you can increase it. Touch the chest to clear your inventory, and click the pickaxe to sell everything in the chest.