Instructions
Wander around the surface until you find a tree. Left-click on it to attack it with your fists. After you've hit it enough times, you'll tear off a log. Tear off two more logs.
Open your inventory. Place the logs in the crafting box. This gives you twelve planks. Fill the crafting box with planks to get a workbench.
Equip the workbench and then right-click to drop it. Right-click on it again to use it. Place two wooden planks in the crafting grid, one on top of the other. This produces four sticks.
Fill the top row with wooden planks. Place a stick in the middle grid and another stick immediately beneath it. This crafts a wooden pickaxe.
Equip the pickaxe and then left-click on the ground to start digging. At first, you'll dig up only dirt, but after a short distance, you'll start digging up cobblestone. After you destroy a cobblestone block, a small cube will float in its place. Touch the cube to take the cobblestone.