2FA adds a 6-digit code from an authenticator app (like Google Authenticator) on top of your password. To enable it from My Profile:
1. Click Enable 2FA
2. Scan the QR code with your authenticator app (or tap Show secret key to enter it manually)
3. Enter the 6-digit code your app generates and click Verify and Enable
4. You'll then see a one-time screen with 8 recovery codes — save or print them; they're shown only once

From then on, logging in asks for your password first and then a 6-digit code before you're fully signed in.