Hi Marc,
Welcome to YamahaSynth.com. We moved your post to the MONTAGE Forum as this is more appropriate, given you own a MONTAGE 8 (not a reface).

When you got your MONTAGE in with the Owners Manual was a piece of paper with your Cubase ACCESS CODE and instructions on how to proceed to download a copy of the current Cubase AI/LE/ELEMENTS.

You’ll need that Access Code to get your Authorization (license).

Basically, you are going to go to the web url to download Cubase AI
You will be setting up a MySteinberg Account, and your Access Code will be used to send you a Authorization Code...this is your license to use Cubase (they will email it to you).

Once you are licensed you can use Cubase on your computer (if it ever crashes, blows up or just gets replaced, having a MySteinberg Account will allow you to move the Authorization to your new computer)

If you are working musician who may need to use Cubase on different computers in different locations, you can transfer your license to a USB Key (dongle) that you can travel with. You can put Cubase on multiple computers - the Key allows you to run Cubase wherever you go. If you do not travel to other computers you can forego the Key (dongle) and just authorize your computer to run Cubase.