Installing One Page Express PRO

After completing your order you should have received an email containing a download link for the PRO version. You need to download that - it will download a ZIP file which is the theme package (you don't need to expand it as you will need it as a ZIP file).

Once you downloaded the package, you need to go to WP admin -> Appearance -> Themes -> Add new and click the "Upload theme" button at the top of the screen. Then you have to select ZIP file you downloaded and click install. Then, when prompted you have to activate the theme.

Also, if you have the free theme installed, you don't need to uninstall it as the PRO version is build on top on the free one.