Any Remo Software product from Prime subscription could be activated and used on two computers simultaneously. You would not be able to use the same software on three computers at the same time. If you wish to activate the software on a third computer, you would have to deactivate the software from one of the other computers, download and install the software on a third computer and proceed to activate the software.
In the dashboard of your account, you would have "Linked Devices" option. This would allow you to see all the device/s on which the software/s is/are activated. You need to click on "Unlink" against a device from which you wish to deactivate the software. You could then download, install and activate the software on the third computer using your login credentials.