You have to put the picture on an outside source that allows sharing, first. Some folks add their pictures to www.imagestation.com. Others use www.shutterfly.com. And there are others out there that work as well. Then, you right click on the picture, left click on properties and copy the URL address that comes up. That's what you insert in your post as an IMG......by clicking on the IMG Button and pasting the address there.

Hope that helps. I do think the pictures need to be in .jpg format.