Hello Kevinnev73-aol-c,
Welcome to the Community page,
If you click on the main cog wheel top right hand side> then under settings click on custom forms styles > click on your invoice template> content > click on the bottom box section on the right hand side> on the left hand side you will see a box that says add payment details and footer> enter your bank details in there> then click done
Then when you go to create and invoice and fill it all out, when you click on print or preview it will show your bank details at the bottom of the invoice page for your customers to see.