Per Noalt's answer is correct. However, if you want the snap-in mentioned in the title (Users and Computers), you'll also have to run these commands at a command-line afterwards, as an Administrator:
dism /online /enable-feature /featurename:RemoteServerAdministrationTools-Roles-AD-DS
dism /online /enable-feature /featurename:RemoteServerAdministrationTools-Roles-AD-DS-SnapIns
Note - I had to run these in order for AD Users and Computers to show up, as they were disabled on my computer after the install. This might not be the case for all users.