Search for the customer you wish to link to this new account, select their name, and click "Cust Details."
Under "Accounts" click "Add New" from the dropdown menu.
A new window will popup where you can enter in the account information. Make sure you check the "Charge Authorized" box. A credit limit is optional. When you have entered everything click Save.
The new account will now be available for selection in the dropdown.
Be sure to click Save & Close when you are done.