[*img*]http://img.timeinc.net/time/europe/2006 ... zzurri.jpg[*/img*]
Of course, take out the asterisks, but that is the format for images - the html tag [*img*]lets the computer know that the following url points to an image and the end tag[*/img**] tells it to end the command.
The image has to be on the internet already. With MacOSX you can do that very simply with your own computer or you can upload you images to Photobucket or ImageShack.
Files other than images work the same way but you need to use the command to point to the file location.
Let me know if anything remains unclear.