By default all Google groups are private. The following steps detail how to make a group public. There are three settings within the basic permissions that will allow your group to be public. They are: View Topics, Post, and Join the group. These instructions assume that you have already created a group.
Go to Permissions on the left side of the screen and select Basic permissions.
View Topics - this setting determines who can see the web version of your group. If you want this part to be public: 1. Click the View Topics drop-down and select, Public.
Post - this setting determines who can create messages and interact with your group. Opening posting to the public may invite spam. If you want this part to be public: 1. Click the Post drop-down and select, Public.
Join the Group - this setting determines who is allowed to join your group. Opening this to the public may invite spam. If you want this part to be public: 1. Click the Join the Group drop-down and select, Public.
Once you are satisfied with the group settings, click the red Create button at the top of the screen.The group will now be public.
To allow public to post in the group follow the instructions listed below.
Navigate to the group and click on Manageon the right side of the screen.
Click to expand Permissions.
Click on Posting permissions
On the Posting permissions screen find Post. Select Public on the groups of users.