If you don't know how to install

1.This install process for android 7 lower

 version there are click the "application" then click the install(that directly forward you in this button) allow it then you will "install the application"

2.if it's not work then go the "setting" then go "siqurity" the find "unknown sources" then "allow" it then you will "install the application"

3.This is for android 8 or higher 

Simple click the "application" then click "install" it's showing "allow unknown source" click allow then you will "install your file"