This part has been done in GUI in my case, however, better is to do it in PowerShell and here are the steps. To install DC on Windows Server 2012 we just need to:

1. Install windows feature Active Directory Domain Services
Open PowerShell and type “Add-WindowsFeature AD-Domain-Services” Enter

Add-WindowsFeature AD-Domain-Services

2. Install windows feature DNS
type “Add-WindowsFeature DNS” Enter

Add-WindowsFeature DNS

3. Install windows features for administration (RSAT*)
type “Add-WindowsFeature RSAT*” Enter

Add-WindowsFeature RSAT*

Once windows features are installed, we can promote computer to DC:
4. Install new DC to existing forest / domain / Site
DC should be GC as well.

Install-ADDSDomainController -CreateDnsDelegation:$false -DatabasePath 'C:\Windows\NTDS' -DomainName 'domain.local' -InstallDns:$true -LogPath 'C:\Windows\NTDS' -NoGlobalCatalog:$false -SiteName 'Default-First-Site-Name' -SysvolPath 'C:\Windows\SYSVOL' -NoRebootOnCompletion:$true -Force:$true -Credential (Get-Credential) -ReplicationSourceDC Server2.domain.local

Next step is to recover Exchange server on the DC.