This is a simple program intended as an exercise.
To move your character, use the WASD keys and the Mouse. Scrolling the whell adjusts camera sensitivity and holding down left shift will increase your movement speed.
If an item you point at shows an outline, it is capable of being picked up. Click with the left mouse button to add it to your inventory. Click with the right mouse button to open your inventory. Clicking one of the buttons with the left mouse button will drop the item. Clicking again with the right button will close the inventory.