It's probably confusing it an existing game an your phone, it happened to me, I've uninstalled the other game to install this (SCP Affection, was what it was confusing it by the way.)
Just the Appstore, and then use long press on this app's apk in your files and choose open with it'll give you other installers to choose from, pick any other then the default one, it'll open the app that this one is confusing with exit and uninstall it to install this one (or wait for a update that fixed the issue)