Hello!Pro Tap Live is region locked. This means that it is only available in Japan. To play on a non-Japan device you must jump through a few hoops.
Android based phones have it a bit easier, since the system allows to install files outside from the PlayStore.
- Find the latest .apk file online and put it on your phone. The .apk files can be found in fan forums, such as Hello! Online.
- Download qooapp here, install it on your phone. Using that app, search for Hello Pro Live. Install it.
You can also install the app while using a proxy (like TunnelBear). Choose Japan as your proxy location, get your .apk file and install it.
Phones and devices with iOS as operating system (iPhone, iPad, etc.), you will need a Japanese account for the AppStore. This asks for a Japanese adress. There have been cases where user took the adress of a hotel etc. and it worked. Once you've created your Japanese account you can download and install the App from the AppStore.