Aperture install

You don't, in a word. There is no installer available from the App Store or Apple that will install on 10.14. If you have an install disk, the version on that won't run on 10.14.

Which version of Aperture created your Aperture Library? Did you previously use Aperture 3.6? If Aperture is in your purchase history at the App Store you can download it from your past purchases. This should install Aperture 3.6. And you should be able to open your old Aperture Library this way to be able to compare the items that do not transfer perfectly to Photos, like hierarchical keywords, smart albums, brushed adjustments.

If you can find a copy of Aperture 3.6 on a backup disk of your previous Mac, you can simply copy it over. You photos should all have been transferred, but there may be differences between the smart albums or missing metadata tags. (Notes on Migrating an Aperture Library to Photos for Mac, 2019 version)

If you own an AppStore version of Aperture, check the AppStore here:

You are of course aware that Apple discontinued all support for Aperture in Oct of 2014.

I think your chances now of finding anything to install Aperture with now is non-existent.