Before you can download a paid app, you must set up a billing arrangement.
Price/Install button
Indicates the cost or install for free apps.
From the Home screen, tap the Play Store icon .
Tap a category from the homepage or tap the Search icon (at the upper right of the screen) to search for an app.
Tap the app you want to open its details screen.
Tap INSTALL or the Price button to download the app.
If you agree with the app's access requirements, tap ACCEPT.
The app will be downloaded and installed.