There is only one built-in skin for Voice Changer Software 8.0 Diamond on its initial release. More skins may be added in later builds.
Step 1: Click the More command in Skins menu to visit Add-on page
Step 2: From the list, select the skin you want to download, click the Download link next to the item name. This will open the download page of that skin.
Step 3: Click the Download It link below the item name. This will popup the File download window. Choose Run or Save to start download the file.
Choose the skin file you want to install (file in .exe format), double click on it, click Next three times, and wait for a few seconds. When the last screen popups, click Finish to finish the installation process.