When you log in to a new device/session, you must verify the login and connect it to cross signing and secret storage to access your backed up encryption keys for historical messages. This assumes you already have configured cross signing, see Set up Cross Signing.
Log in to Element with your username and password
Choose one of the methods below for cross signing
Use another login
Login is here demonstrated on Element Android
Verify this login
Scan with this device
Use Security Key