Go to Settings > General > VPN > Add VPN Configuration.
Select IPSec, then enter the following information:
Description: Enter a description of the VPN connection.
Server: Enter the server address.
Account: Enter your account name.
Password: Enter your password.
Group Name: Enter the group name.
Secret: Enter the shared secret.
Tap Save.
To connect, go to Settings > General > VPN and toggle the VPN connection on.