The way you did it was the easiest. You didn't need to upload it to the gallery if you're attaching it here as an attachment. Either one or the other
Just to show you, if you already have a picture in the gallery then place the address to the photo by putting it between [img] [/img] tags.
YOur gallery link is
http://www.orchidboard.com/community.../500/mexi1.jpg
now if you put that address between the [img] tags you'll get a pic like so:
