If you want to do your regular Active Directory stuff on a Server 2012 member server you must first install that specific Feature. It’s more or less the same as on Server 2008 R2 but I will sum up both ways you can install it.
1. To install Active Directory Tools on a member server with the new “Dashboard” just click on the icon left on the taskbar (where the start button used to be) and click “Add Roles and Features wizard”
In Features, expand Remote Server Administration Tools and Role Administration Tools, expand AD DS and AD LDS Tools, and then click AD DS Snap-Ins and Command-Line Tools.
2. To install Active Directory Tools on a member server with Powershell just open a Powershell prompt with elevated privileges and enter the command:
Add-WindowsFeature RSAT-AD-PowerShell, RSAT-AD-Tools and hit enter.
Now you can start DSA.MSC from the run box as usual.