1. This is not a standalone app, you need to install v3.39 above(or LATEST) version of GO SMS Pro app in order to apply this theme. (Search “GO SMS Pro” to download)
2. To apply the theme within GO SMS Pro, download it from Menu->Theme (or Plug-in UI->Theme shop). After downloaded, it will displayed in "Installed Theme" Tab, click and apply it.
3. This is a free theme, just enjoy it.
GO Sms Pro theme gosmstheme