the GPU change works automatically in most cases. If not, you have to start the neXt with your Intel graphic card, deactivate it and then start it with your Nvidia graphic card and activate it again.
This is the typical workflow while changing an computer: Start the neXt on the old computer, press esc, change to License tab, press key o, press on delete license. After this you can activate the neXt on your new computer.
Yeah it should do it automatically, as it did with mine from igpu to nvidia gpu.
This is the other reason why I chose to buy the Next CGM simulator. You get 2 licences. I have the other licence installed on my backup pc, just incase my main pc crashes for some reason.