Two-factor authentication (2FA) is available under Settings → Security. Scan the QR code with an authenticator app (Google Authenticator, Authy, or similar) and enter the six-digit code to confirm.
Once enabled, every login asks for a fresh code in addition to your password. Save the recovery codes shown at setup — they're the only way back into your account if you lose access to the authenticator app.
2FA can be disabled from the same settings page if you re-authenticate first.