Select "Sync or import your wallet", on the initial launch of MetaMask Mobile.
- Open the extension
- Go to Settings > Advanced
- Click on "Sync with Mobile"
- Scan the QR Code to start syncing
Alternatively, you can tap "Import using seed phrase" or go back and tap "Start exploring" to use a new wallet.
NOTE: Only accounts tied to the seed phrase, and loose accounts imported via private key or json will sync. If you have a hardware wallet connected to MetaMask, that will not sync at this time.