To add the Assign credits to customer action to the workflow, click on the "Assign credits to customer" icon.
To set the parameters, click on the node.
The settings window will appear.
Insert the name of the node.
Select a credit type.
Choose the type of credits assignment.
Insert the number of credits, that will be added to the customer account.
Select a partner.
When everything is set, click on the "Confirm" button.