I am not able to find Remote Desktop Client in my program list or searching with Spotlight (I am asked to turn off Remote Desktop Client to install Adobe Flash Player, and therefore I am not able to install new version of the flash player)
You won't as it's not an app as such but rather a service. If you want to 'see' it launch System Information in the Utiltiies folder and select Applications from the Software section in the sidebar. Be patient as it will take a while to build the list.
To turn it off launch System Preferences, click on the Sharing Preferences Pane and untick the option.