How to turn on notifications for groups? I want my group members to receive a notification if there is a new post in the group.

You can define if you want the members of a group to receive a notification when there is a new content posted in the group. You can do this by clicking on the checkbox when you are creating a group. You can also turn on/off notifications for a group by going to the group's page, clicking on the (...) button> edit> and clicking on the checkbox.