It is best practice to let tenants set up their own auto pay. However, you can do it as well from the back end. Please see steps below.
Please note: The below instructions only work if a payment method is already in the system.
Link for creating payment method - https://propertyvista.zendesk.com/hc/en-us/articles/115000302747-Creating-Payment-Method
Step 1: Click on tenant in question.
Step 2: Click on Edit.
Step 3: Go to Auto Pay tab and click on the "+" sign to add a new Auto Pay.
Step 4: Click on the drop down in Payment Method and select the method.
Step 5: Once done, click save