How to install old Guitar Rig 5 in Cubase 12 pro?

First of all Guitar Rig is an effect and not a instrument. Therefore in Cubase 12 Pro you will need to ensure that it is included in the effects list using VST Plug-in Manager. If it does not appear in the list, it can be added by searching in C:\Program Files\Native Instruments\VSTPlugins 64 bit (I am assuming your are on Windows). Guitar Rig 5 should now be added to your list of available effects.

If you want to add the Guitar Rig effect to a track it can be done 2 ways:

1. Instrument Track - Add Guitar Rig 5 as either an insert or send effect.
2. Audio Track - Set the routing out to the Guitar Rig effects track.

Hope this helps.