I'm pretty sure you will have to use some external imaging service. There are probably others besides photobucket, but I have used photobucket and it is extremely easy. Somewhere on this forum is exact step by step instructions. I can't remember off hand where they are, but I have seen it a couple of times. Try reading some stuff on here. It is saved at the top of a list of posts, probably under amphibian photos.
They can be hosted anywhere online, I've used pics from my facebook in the past but PBucket is easier if you're not as tech savvy. The guide to using photobucket may be outdated, if so I shall add a new one shortly.