There should be an 'accept outside application sources'-option in your phone-settings somewhere. Most likely not expressed in those exact words, but it should be in there somewhere.
Or you could just download the .apk-file to your 'com-pu-tor' and transfer it from there, to a spot where you can then locate and install it.
-But most of all, be careful.. as there is a not-insignificant chance that your innocent mind could get corrupted by exposure to 'titties and ding-a-lings' depicted in this game.