Groups are created for employees with shared interests or a shared working relationship. For example, there are departmental and job groups, project groups, and social groups. For the groups, depending on the privacy settings, you can become a member yourself and/or be invited.
Privacy settings groups
Open groups are for public use and can be identified by the icon of an eye.
Closed or hidden groups are groups where the information is shielded from non-group members. The group administrator of a closed group can determine how people can join the group: by requesting access and/or by invitation. This option can be recognized by the padlock. 
Find your group
Navigate to the group you want to join. You can find the group under the menu under Groups. Then click on All groups / Open groups and use the filter, or scroll through the whole list and/or search for the right group using the search function. Then choose the group you want to join.
Becoming a member of an open group
Everyone can become a member of an open group. Go to the concerning group and click on Become Member. You now are directly a member.
Becoming a member of a closed group
If you want to become a member of a closed group, there are two options:
- You can go to the group page and click on Request Access to the Group. The group manager then needs to accept your request, in order for you to become a group member.
- There are also closed groups where it is impossible to request access. For these groups, you need an invitation. Thus, youshould ask the manager for an invitation.
Leaving a group
If you don't want to be a member anymore you can leave a group. In place of the membership buttons, three dots will appear. Click on these three dots and choose for: Leave group.
TIP!
A complete explanation about the group page (with screenshots and instructions) can be found here.