If you’d like to use a 3rd party UPS account for just one order
On the orders page hit the pencil in the Shipment Info section and you’ll be able to enter the 3rd part UPS info you’d like to use for a particular order. If the order doesn’t have a UPS method, change to UPS, refresh the page and hit the pencil in the Shipment Info section
To ship many orders on a 3rd party UPS account
Create a new profile for your warehouse at https://app.shiphero.com/dashboard/warehouses then add the UPS account to that account at https://app.shiphero.com/dashboard/shipping-carriers and contact support to add 3rd party billing to that profile.