My current desktop is Fedora15. I need to access my desktop from another fedora15 desktop using remotedesktop viewer. Please help on this
The Fedora project has some documentation that can help you out.
It boils down to installing a VNC server on the desktop you wish to view, and a VNC viewer on the desktop you wish to view it from. Fedora makes this easy with the "Desktop sharing" tool.
If you need to access a machine over the internet, make sure the necessary ports are open in the firewall, both on the Fedora box and on the router (if any).
Under the System pull down in Gnome, launch the Remote Desktop App, System -> Preferences -> Remote Desktop. From here check the allow other users to view your desktop. Also set the security and notification sections accordingly.
Once you're setup your Fedora system so that it will accept remote connections you can use a remote desktop client such as Vinagre, again a Gnome app, from the Applications pull down, Applications -> Internet -> Remote Desktop Viewer. Once this application comes up you'll need to open a connection to a remote server.
In the connection dialog select VNC for the connection protocol and put either the remote servers name or ip address and click connect.