Here you can specify which payment methods will be available for the given shipping option. To add payment methods, click the Add payments button and check the boxes next to the appropriate payment methods in the displayed selection dialog. Payment methods can be removed from the shipping option at any time using the checkboxes in the list together with the Remove selected button. You can also remove all listed items at once by clicking the icon and performing the Remove all action.
Please note that payment methods can be managed in CMS Desk -> E-commerce -> Configuration -> Payment methods.
More resources concerning payment methods can be found in in the Payment methods topic in the Managing your store -> Orders section of the E-commerce Guide.
Further information about shipping options can be found in the Shipping options topic in the same section of the E-commerce Guide.