To add a new payment type, go to:
Start Page > Admin > Common Catalogues
From the Catalogue list open Payment Types. This will give you the option to create a New Payment type.
There are two options to proceed; you can either click the + sign next to New Payment type... situated within the category list, or click + Add new... in the action section on the right of your screen:
Next, enter the new payment type into the Name Section and Save:
The new payment type entered should now appear within your payment type list:
And show up in your Payment Method options when taking a payment: