You can customize Payment Methods to give you additional options when it comes to recording Payments for Clients. To access the list of Payment Methods, go to Settings > Payment Methods. That screen will look something like this:
To add a new Payment Method, click Add Payment Method. To delete an existing Payment Method, click the red "X" to the right of it. To edit an existing Payment Method, click the name or pencil icon. From the edit screen you can inactivate any Payment Method you do not need by un-checking the box next to "Active".