Tenant ID is the domain of your program (for example if your Trackdesk URL is "https://my-program.trackdesk.com/" then your Tenant ID is "my-program").
This credential is needed for some integrations, it's your unique identifier within the Trackdesk platform.
If you use our custom domain feature and not Trackdesk's subdomain to access the platform, you can find your Tenant ID on the Settings main page.