To select ShipCompliant as your Sales Tax Ratte Source, you will first need to open a ShipCompliant account (fees apply). Then follow these steps:
First enable ShipCompliant in Nexternal (Settings / Compatible Software / Alcoholic Beverage Tools / ShipCompliant). For more information about ShipComplaint and a Downloadable Setup Guide, reference this article. Then navigate to Settings / Sales Tax / Third Party Sales Tax Provider, and pull down to ShipCompliant.
To get the rates you expect for each location, you will need to make sure that you have made the correct tax preference selections within ShipCompliant - please contact ShipCompliant with any questions relating to that.
Further, if a state requires that you charge tax on shipping as well as products, you will need to check the appropriate "TS" boxes within the Nexternal tax tables.