To order printing online, you can now use the PDQ Print Portal.
The first step is to acquire an account, which you can get by sending an email firstname.lastname@example.org. They will send you a username and temporary password.
Now, you can go to http://www.pdqprint.com to access the portal. Click on the Customer Login and use your username and password that was provided. If it is your first time, choose a more permanent password that you will remember.
Here are more explicit instructions.