If you want to put up photos from your Facebook, or post a Youtube video, it is very easy. Here is a Youtube showing you how.

I haven't found a simple video for uploading one of your own camera photos to a image hosting website and from there getting its link. It's roundabout for sure. I think it is necessary for the image to 'be on the Internet' somewhere because the files can't be stored on everyone's PCs as that would clog everything up... they have to be avail online and Steemit app just fetches them.