In the Joust app click on the "Bill Pay" icon and follow the steps to begin setting up the bill pay feature. You can search for your billers using the search bar and link your account by using your biller's credentials (Joust never stores your credentials).
Once you've set up a few billers you can go to the settings pop-up in the bill pay screen and then click on payment methods and add a new payment method. It's easy for your to copy and paste your Joust account and routing number by clicking on the My Joust tab, then the details bar, and clicking the copy icon next to "Account No." and "Routing No."