My apologies for the confusion, Jackson. To authenticate against the TD API in a workflow, you will first need to create a workflow web service account in the Admin application. You can find this by going to Admin > Ticketing Applications > Select the application your workflow is associated with > Workflow Web Service Accounts > New. From here you can add a username and password that you use to login to the API.
The next step is to associate that account with a workflow web service. To do this, go to Admin > Ticketing Applications > Select the application your workflow is associated with > Workflow Web Services > New. From here you can set the base URL and select the account you just created from the "Authentication Account" dropdown.
You can now associate that web service with your ticket workflow steps, and all authentication will be taken care of for you by the workflow process itself. Again, my apologies for any initial confusion. Let me know if this helps. If you have any additional questions, feel free to email me at email@example.com.