How to install .key files?

I have just installed a program, and while trying to install the .key files, I recieved an error message, shown in the screenshot below. It told me it was not a registry script and I could only import binary files from regedit. So I went into regedit and File>Import, and found the keys I wanted, but it told me that the key will be restored on top of the key that regedit was on when I opened it, deleting all subkeys. Obviously I don't want to do this, so how do I correctly install these?

only keys I use go in a specific file for that software and on run the software finds it and loads to registry.
open key in txt editor open registry where key is compare may be you can modify.
back up reg first of course

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