How to remotely access another computer?

 team-viewer, AmmyyAdminn, AnyDesk, VPN 

I have access to another computer  through RDP.

The easiest way is to use 3rd party software like team-viewer, Splashtop and AMMYY Adminn you can access it anywhere over the internet.You could take advantage of Wake-on-LAN to turn on your PC over the Internet. This would allow you to leave your PC off except when you want to access its desktop or files remotely.Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else's computer remotely.

the easiest way is to use 3rd party software like teamviewer, vnc or logmein you can access it anywhere over the internet 

or set the desktop you want to access and allow remote desktop but be sure configure the router's port forwarding.