It's unclear what 'API token/key' might actually be here, but the mechanisms for accessing the Geotab API are described in the Concepts section of the SDK here: https://geotab.github.io/sdk/software/guides/concepts/.
Note that the typical method of access is to begin with an Authenticate call with a Geotab database name, username, and password to obtain a returned credentials object and a server path to use it with. If someone has provided you with those instead of a password then the session id portion of it will be valid for no more than two weeks from the time it was returned from the authentication that generated it.
If you have been provided something other than that, I do not know what its purpose might be, and you'd likely want to refer back to its source for clarification.
Thanks,
Ken Wallen
Geotab Senior Solutions Engineering