RDP can not be used as a protocol when connecting TO a Linux machine - there is no RDP endpoint listening on the Linux machine. In order to connect to a Linux machine, you should use either SSH (Secure Shell) for command line or VNC for the full desktop environment.
Read the following article on how VNC works on Ubuntu: https://help.ubuntu.com/community/VNC - I think this covers the basics. You should first install (if you don't have) a VNC server on your Linux box. Then configure it to allow you to log in (as detailed in various links). Once that is done, you will need a VNC client such as RealVNC Viewer on your Windows machine so you can connect to the Linux machine.
First install SSHD (ssh daemon) on your Linux machine and configure it (by default it uses password authentication and port 22). This step might differ between Linux versions.
Then, on the client you can use a couple of SSH clients:
- SecureShell extension for Chrome
- Cygwin (this is the most heavy duty one - it gives you access to all Linux software -including the SSH client - on a Windows machine)
P.S.: sorry for the lack of links, I don't have enough reputation.