post https://api-int.truckstop.com/auth/token
With REST APIs, there are two different API calls to get tokens. These will be the same for both authentication methods, Resource Owner Password for Proprietary systems and Authentication code flow for 3rd party TMS systems (more).
Depending on your setup, you will use the resource owner grant or authorization code grant type. If you are unsure how your credentials are configured, please email [email protected].