At the bottom of this page, there is a button "Download Universal APK" that will download the installation file to your phone. Run the .apk file to go through the installation process. Android might give a warning about "installing from unknown sources". Since you're the wiz behind the curtain, confirm your decision and forge ahead. After that, you should have an Obtanium icon in your apps area.
At the bottom of what page?
Oops! I forgot to paste it! https://obtainium.imranr.dev/