In reply to LJJ77:
Not sure which strapping system you have but the starting point should be getting the crampon to fit the sole of the boot WITHOUT worrying about the straps yet. You need to adjust the crampon's length so that the upright "posts" fit snuggly against the sides of the sole at toe and heel, and the side posts may also need adjusting. Once this is correct, it will be a little awkward to press them on to the boots, but easy enough if you're wearing the boot and step onto the crampon using your weight. If you shake the boots, the crampons shouldn't fall off.
Only then do you need to worry about the straps. There's another thread here which links to some photos which should help with how the straps should look:
http://www.ukclimbing.com/forums/t.php?t=532530. As said, you should be able to get hold of longer ones if necessary.