Process on the Extreme Portal located here: https://extremeportal.force.com/
Step 1: Navigate to Support > Case Management
Step 2: Open a Case with an RMA associated to it. You can use the advanced filters to see all your RMA related cases.
Step 3: Open the RMA tab of your Case and expand the RMA Details section (click the caret on the right side) and locate the "Generate Waybill" link near the bottom of the page.