The Group ID is a unique number assigned to each individual group that you have created.
A Group ID is required when you are setting up a sign up form on your website or setting up a sign up form on your Facebook page. Having the correct ID number will ensure all contacts who sign up using the form are placed into the correct group in the Contacts area.
Information on how to add an online sign up form can be found here
and instructions on adding a sign up form to your Facebook page can be found here
The Group ID can be found in the Group Card. To view the Group Card, start by clicking on the Contacts link on the top toolbar.
Once clicked, it will bring up the Contacts dashboard. Click on Groups which is between Dashboard and Segments.
the overview of all the Groups that you have. The next step is to select which
Group ID that you would like to see. Hover over the Group that you require
until it is highlighted, then click on the Edit icon that
Once you click on Edit, the Group Card will appear and here you will find the Group ID for that particular group.