Fleet connection happens during setup
Fleet is CoW's multi-device account plan. On a new device, choose Yes when setup asks whether you have a Fleet subscription, then verify your existing account.
Restart setup if you skipped it
If setup is already complete, remove CoW from that browser and reinstall it to begin the setup steps again. This lets you connect the browser to your existing Fleet collection.
See how to set up CoW on a new browser or device for the full process.