1) Create a new payment form (or find the form you would like to edit.)
2) Find the Frequency section and choose Decided at Checkout from the drop down menu.
3) Choose whether you'd like the form to default to One Time or Recurring. The payer will still be able to pick between the two, but this choice will determine which setting payers see when they first arrive at the checkout.
4) Click the Save & Finish button.