From Wiki

If you need to add a manual commission to an affiliates account for a specific programme, follow the steps below!

Step 1 - Click "Add manual commission" in the merchant interface

Step 2 - Click the drop down for "Commission type" and select bonus

Step 3 - Fill out the details!

If this is a prize for a promotion then leave the sale value as "0.00".

Take care with entering the commission (bonus) value as once you have submitted you can't reverse it if it's wrong!

For a prize the order reference can be left blank. The info for Affiliates should be filled out as when ticking the "send affiliate email with commission details" this information will be sent directly to the Affiliate.