Downloaded the app to your phone from the button above.
From the downloads section of your phone (or the successfully downloaded
notification) you can open the file and will be prompted to install.
Most phones will do this without arguing, but depending on the version
of the Android operating system you are using there may be a security prompt (install blocked).
Go to: Settings Security
Here you will find a section called "Allow Unknown Sources".
If this is checked you will be able to download and install apps
from sources that are outside of the Google Play store.
Once the updated setting is active you will be able to install and use the app.
If you want you can turn on the security setting again without it affecting the app.