Here's a quick guide on how to receive payment for an invoice in DigitBridge.
The first thing you will need is an invoice you want to pay. Typically, invoices are created when a sales order has been marked shipped, but you can also create an invoice manually (See: How do I create an invoice manually?).
Note: This process is only for non-digital sales for customers not connected with any sales channel. If you enter a customer that has been connected to a channel, the following error will appear:
Clicking Yes will take you to the Settlement File Payment Management screen.
Next, you will navigate to the Receive Payment tab (under Accounts Receivable). 
Click on Add.
Enter in the customer number and click Load All. All open invoices for that customer will appear.
Select the one(s) you want to process payment on. You will notice that, as you select them, the amount in the New Balance column automatically shifts over to the Payment column.
You are able to manually adjust the Payment amount, which will then automatically adjust the New Balance amount accordingly. This allows you to partially pay certain invoices.
You will also notice that the Amount Received and Total Payment values have updated.
Once selected, update the Paid By/Credit field to the payment method you desire (if you need to process a credit card payment, check out this article).
Once you're done, click Save.
Click Yes.
If the invoice was paid in full, the status of that invoice will update automatically from Outstanding to Paid.