After downloading, you will typically find a .theme file and a corresponding folder of the same name.
By default, Windows 7 does not allow third-party (non-Microsoft) themes. To enable them, you must use a "Universal Theme Patcher."
: Look for UltraUXThemePatcher or similar tools often bundled with Kuyhaa downloads.
If you are trying to make a newer version of Windows look like this, you might need additional software like WindowBlinds to support legacy Windows 7 styles.