Require Agreement To Order Instructions
Have your customer accept your specified terms upon checkout.
1) Go to the Settings Page on the left-hand menu.
2) Scroll down to the bottom right to Order Instructions.
3) Type the information that you want the customer to agree to in the box and then check the "Require Agreement To Order Instructions" circle!
4) Now, before the customer checks out they must check the "I have read and accept the above note from..." box.
Example at checkout: