Navigate to the Main page of your project. In the Output Settings section under Submittals, you will have a drop down that will allow you to select any Transmittal Templates that are available for your use. Find the one you want and select it - both PDF and Excel versions. You can select different transmittals to be used for your Customer (shown as Acme in screenshot below) and Sub-Supplier. Note: Internal/3rd Party Transmittals will use the selection you made on your Sub-Supplier Transmittal. Remember to click Save Project when finished!
For more information on working with Templates please check out our video: Templates