Here are the steps in summary (click this link for full Technet guide):
Step 1: Install WSMT
Install WSMT feature using server manager on the target WS2012 server.
Step 2: Register and deploy WSMT
Start an elevated cmd prompt from the WSMT tool. Create a deployment folder that is accessible to the source server. Depending on the OS of the source server, an example of the command for WS2012 (default on "C:\Windows\System32\ServerMigrationTools\") would be:
SmigDeploy.exe /package /architecture amd64 /os WS12 /path [deployment folder path]
Copy the deployment folder to the source computer. Register and deploy the source computer by running .\Smigdeploy.exe
Step 3: Move local users and groups
To preserve local permissions, you may need to move the local users and group first. To export from the source computer:
Export-SmigServerSetting -User All -Group -Path [storepath\UsersGroups] -Verbose
To import into the target server:
Import-SmigServerSetting -User All -Group -Path-Verbose
Step 4: Start file moving
Before moving, permit both UDP 7000 and TCP 7000 on the windows firewall. On the target computer, start the reciever:
Receive-SmigServerData
To begin file transferring, run the following WSMT cmdlet on the source computer
Send-SmigServerData -ComputerName [DestinationServer] -SourcePath d:\users -DestinationPath d:\shares\users -Recurse -Include All -Force
You may want to observe any errors at the progression update on the command prompt.

