The bag icon at the top right corner of the page is your cart. The number will tell you how many items are in the cart.
From here, you can edit quantities of the items in your cart by clicking the bag and pressing the + or - buttons on the cart dropdown.
If you want to remove an item completely, press the "x" button on the right of the item you want to delete.
If you decide that you want to checkout, the "Proceed to Checkout" button at the top of the cart dropdown.