What file format are the graphics in?
If you're trying to load graphics with a transparent background, they must be in PSD, GIF or PNG format with an alpha channel.
If you've got Photoshop or Photoshop Elements, you can manually remove the the background and save it in one of these formats.
It's a bit hard to describe, unless you know Photoshop. But you need to open the file and turn the background into a layer. Then you need to select the background (with the Magic Wand tool) and delete it, then save the file as a PSD.
I show you how, with illustrations, in my Steve's Tips article at Muvipix.
Or you can post the graphic here and maybe I or someone else can do this for you.
Thank you for your help. This should work if not it will be from human error, namely me.
Probably not so much "human error," on your part, as it is a difference in graphics format and the preparation of these graphics.
If you can post a URL to these particular graphics files, we can tell you exactly what you need to do to use them in your video.
As Steve points out, almost everything is possible in Photoshop (or PSE), and the method will be defined by the format of the individual files.