The Multiboot image is probably the best one to install unless there is a problem with the receiver. You will need:
USB drive with free space of at least 500MB
A folder named exactly downloaded_images installed on the usb drive
A multiboot image.
To install in the receiver:
Prepare the usb drive by placing the downloaded Zipped multiboot image into the folder on the usb drive named downloaded_images.
Insert the prepared usb drive into the receiver, then reboot the receiver to make sure the drive is visible for the receiver to use.
Use the receiver menus and go to, then enter the Flash image menu (Menu--->Setup--->Flash image).
Highlight and press OK on the downloaded images in the Flash image menu. Highlight and press OK on the image you prepared and want to install. Follow onscreen instructions.
If you select a slot to install that has with backup, then a settings backup will be made and you will be prompted if you want to install this backup during image installation.
Hope this explains it well enough to get you started. Really a simple process after you do it a few times.