The bridge is the way for you to activate your Urbit planet. You have bought an Urbit planet and you can see the NFT in your wallet, but what now? You need to produce a cryptographic key that you use when you install Urbit on your computer. With this key, you are identified as the Urbit user with the key’s ID. Without this identification, you are not part of the Urbit network.
The Urbit Bridge is available here.
Be sure to follow all of the instructions carefully – not doing so could make your ship (planet) unusable.
Once you have your key and you have downloaded the Urbit software – ONLY DO THIS FROM THE OFFICIAL URBIT SITE – you are ready to activate (boot) your planet and join the Urbit ecosystem.