Add a windows domain user to a computers local administrator group remotely

To Add a windows domain user to a computers local administrator group remotely

first download and install PsExec from

https://technet.microsoft.com/en-us/sysinternals/bb897553.aspx

open command prompt

use psexec to connect to computer

psexec \\computer_name -u \domain\administrator -p password cmd

a command prompt of the remote computer will open on your computer

then type in the command prompt

net localgroup administrators domain\user /add

should return command completed succesfully

Done.