If you have sharing privileges, you can use the Share button at the top of the group page to post the group on a social networking site such as Twitter, copy a short URL of the group and paste it into an email or website, embed the group into a website, and create an app with the group.
Share groups you own with everybody
If you have privileges to share groups outside the organization, you need to make your groups public before others can find them. To do this, select public as the status for the group. You can only embed groups that are public.