if you download the apk you do not need anything else. but your phone needs to be allowed to run 3rd party apps, since this isn't an official google app store product.
if you don't have that allowed in your settings, it will not work, of course
I do not know, because I do not know what phone you have
But what you can do is find out what phone you have, and then you type into google search engine: "How to allow third party apps on my XPhoneX" googling issues usually solves a lot of problems
