To help make re-ordering easier, you can designate an address to be your default shipping address. This will be what auto-loads for you during the checkout process.
You can always edit or add a new address during checkout, this will be just what is pre-emptively entered to save you a step!
To set up a default address, you will click Edit next to the address within the Address Book section of your Dashboard. From there, click the box next to "Set as default shipping address" and then click Update Address.
Once the page reloads, you will be able to see which address has been selected as the Default Shipping Address.
To remove a this Default Shipping Address designation, you can repeat the steps by clicking Edit, and then unchecking the "Set as default shipping address" box, and clicking Update Address.