After you've created the service, its status is in a Not Configured state, and you must enter the credentials provided to you for your VPN.
You will need the VPN's host name (Server Address), your account name, and your password.
If your company uses a group password or certificate, click on Authentication Settings. Fill in the information as provided by your organization, and click OK:
You will then connect to your corporate network by pressing the Connect button. The most common issues when connecting via VPN are usernames and passwords. If you're not sure you're entering them correctly, you can copy the password from a document and then paste it into the field. To disconnect from the VPN, you can either go to System Preferences->Network->VPN Service->Disconnect, or use the menu in the upper right hand corner of the menu bar as shown below.
Using the built in IPSec configuration, OS X easily connects to Cisco Corporate VPNs using the above steps.