Step 15: Select the “Authentication Methods” tab and click “Add”. The “Edit Authentication Method Properties” window will appear.
Step 16: Select “Use this string (preshared key)” to protect the key exchange and enter your pre- shared key string (for example, mypresharedkey).
Step 17: Click “OK” to return to the “Edit Rule Properties” window, and click “OK” again. The “Edit Rule Properties” window appears.