For one computer or many?
Probably a better way but you can login with account and you will get the SID.
Use a script such as https://gallery.technet.microsoft.com/scriptcenter/5dc1e9f8-ec28-4f2e-aeea-65f6589afac5 to add SID to Remote Desktop Users
It's just for one computer.
My team will play around with the scripting solution some more and post some updates later.