Click on the link below:

http://hangouts.google.com/start

This will create a standard Google Hangout that you can invite your friends to. Copy the permanent link to the hangout that is provided in the pop-up window. You can put this link in a page or forum on your group. Group members can then click on the link to access the hangout. You can also associate the link with the Google hangout image (below) to make things more attractive on the group page.  

Note for first time Google Hangout users

You may want to include the following information under your Google Hangout link for first-time users:

If you have never used Google hangouts before, you may be asked:
1) to download a plugin before accessing the hangout, and/or
2) to allow Google to turn on your webcam and microphone.