Go to Configuration, then Integrations and select HaloPSA API. Click View Applications.
Click New to create a new API application with the following details:
Authentication Method: Client ID & Secret (Services)
Login Type: Agent
Agent to Login as: the TimeZest agent you created in the previous step.
Select the Permissions tab, and select all as the permission.
Before you click Save, copy the Client ID and the Client Secret to somewhere like a text document, as they will not be visible later, and will be needed in the next step.