If the group doesn't exist yet, you can create it.

Add Members to a Group

Select "Active teams & groups" and select the group you want to add the users to.

On the teams panel select "Members"

Select "View all and manage members"

Select "Add members"

This will bring up all active users in the organizations roster. Here you can select all users you would like to add to the group.

At the bottom of the list you will find the add button. When you have selected all required users, select it.

Now you will see the updated users list for the group. Here you can confirm you got all the additions.

Remove Members from a Group

To remove members from a group, in the same panel where members are added, select the members to be removed. Once they are selected, the Remove as member feature will appear at the top. Click Remove as member and then confirm.

After confirmation, the membership is updated.