I am at v 1.8.41 and want to get the upgrade then add the second copy to new faster computer. I wont be using the older computer but don't know how to get version 2 on the second computer for the upgrade price.

You can activate your Reefmaster license on two PCs. If you still have access to the old PC you could upgrade on it, then install and activate the license on your new PC. I would then deactivate the license on the old PC to free it up.