How to add a device to a sync chain using a sync code

First find your 24 word sync code from a device already in the chain or from a backup (you do have it backed up, right?), or create a new sync chain.

 

Then on the computer you want to add to the sync chain open Brave and go to Settings->Sync (or navigate to brave://settings/braveSync/setup) and click I have a Sync Code.

 

On the next screen enter the sync code from the first device, then click OK.