Hello and welcome to the Foreman community.
The token is used as it was a regular user password. It works both in UI and API. No extra field or parameter needed. So instead of a “admin / changeme” you can login using “admin / $thetokenvalue”.
It would be awesome to describe this in our manual Foreman :: Manual, if you’re interested in contributing to our documetation, you can create a PR against this file, it’s simple markdown.
I hope that helps.