You can add as many addresses as you like to your customer contact. You can do this while you are in the process of creating a new customer or going to the customer database to edit an existing customer's information.
Scroll down to the address section in your customer's information form. Click the '+ address' button below the current address(es).
A blank address field will appear below the first. Enter the new address information as you normally would. You may add as many addresses to a customer as you need, by repeating this process.
Make sure to select the address that will be used as the billing address by clicking 'billing address' on the right hand side of the correct billing address.
You also have the option to delete an address by clicking the 'X' on the far right hand side.
After you have finished entering the new address(es), simply click 'update customer' in the bottom right corner to save the changes.