No, you don't need to install any other software apart from Remo MORE on your iMac to add it to Remo Cloud.
You just need to install Remo MORE software on your iMac, launch the software and click on "Cloud Control". Now, you would be redirected to the Cloud Control webpage. Here, you need to login in to your Remo Cloud Account. If you do not have one, please create one in order to have your personal Cloud Account. Now you could click on "Add Device" and add your iMac to your Cloud.