Permissions question

I have a new group coming into the business that will be responsible for 
desktop sup****t. We would only like them to have permissions to add a 
Workstation to the domain and to change user passwords. I am having
trouble 
figuring out the permissions and the best way to apply them to the new
users. 
I have already added the user's to a global group where they are the only 
members.

any suggestions would be greatly appreciated