I live in a country where Tor services are blocked. One of the ways to use tor again would be by using Tor Bridges(obfs3/obfs4). Backbox starts a Tor via anonymous mode and all the traffic from the system goes through it. I would like to know how to add tor bridges so that anonymous mode starts tor and uses the bridge given.
I think this is something specific to Tor relay and the following guide might be what you are looking for:
https://trac.torproject.org/projects/tor/wiki/TorRelayGuide