When Kontat installs it put its Kontact 5.dll drivers in the Native Instruments folder located in Program Files (C:\Program Files\Native Instruments\VSTPlugins 64 bit)
You need to copy the .dll from that folder and put it in the Steinberg (C:\Program Files\Steinberg\VSTPlugins) folder.
Restart Cubase then it should be available in the VST Instruments.
I am currently using Cubase Pro 9 (64-bit).