Once you found the product you wanted to buy, you must choose it's option if possible, set the quantity and click "ADD TO CART BUTTON" :
Wait a little while and make sure that the item is added in your shopping cart as illustrated below:
Simply click the "x" on the right corner of the item to remove it in your shopping cart.
You can edit your cart by clicking "VIEW CART" button
You can update your item quantity with the update button :