As you might have guest, the Hover Grayscale widget converts any image into a grayscale one on hovering over it. The effect can work both ways and all you need to do is to set it up with a few clicks.
After you download the file, look for "Musegain - Widget".zip in your Downloads folder. Double click on the .zip file to decompress it. You will now have a folder named after the widget. Ideally you should move this to another place on your hard drive. Now follow the steps below.
1. Launch Muse if it is not already running.
2. Click the Import Muse Library button in the bottom left corner of the Library panel.
3. In the Import Library Items dialog box that appears, browse to select the .mulib file in your Downloads folder within a folder called after the widget or if you have moved this folder, either search for it or go to the place it was moved to, then click Open.
4. The imported folder (Musegain - Widget) appears in the Library panel, ready for use in the current file. Then drag/drop the widget to your project, set the options and enjoy!