Adding a new admin user will be divided into two actions: first the creation of the new user and then secondly the assignment of the user to the admin group.
Connect to the Windows 1012 Server with Remote Desktop click on little down arrow at the top bar
Select start and then click on the server manager icon (what happened to the small icons?)
In the black bar at the top click on tools and select computer management
Add New User
To add a new user expand Local Users and groups in the tree menu on the left.
Right click on the centre pane. For a new system there is Administrator and Guest listed.
Select New User from the popup window and enter the details for the new user.
Add User To Administrator Group
Expand Local Users and groups in the tree menu on the left
Double click on Administrators Properties
Click on Add to add a user to the group
In the box enter the name of the user and then click on check names. Accept the user.