Thats because you are not in the right folder. You have to be in the same folder where the deb are. If you just start xterm then you probably will be in /home/user/, must likely you have the deb in /home/user/MyDocs, or /home/user/MyDocs/Downloads. Write cd and then some of the places I wrote to find out. ls is a nice command to see whats in the folders. A tip is to write hildon-desktop and then ctrl and i, after that you cant spell it wrong.