First, have you integrated with AD?
In any case, you’ll need to log into the admin console, click on Users / Groups, then on Groups.
Create the groups you want and add the users you want to them. If you have integrated with AD, this is much easier (it will pull over your AD groups…I created a bunch of groups for different departments just for Chat contacts, works great).
Then after you created the group, click on it to edit the details. Under Contact List (Roster) Sharing, choose “Enable Contact List Group Sharing”
Input the name you want to display in Spark in the Enter contact list group name box, and then check the box that says “share group with additional users”
You can then choose “All users” or specific groups you want to share this group with. On my server it’s set to All Users.
If you do this, when you add a new user, just add them to that group (either Spark group or AD group) and when they log into spark their contact list will automatically appear.