Hi, I'm fairly new here too, but I've been posting pics online forever. When you go to post something here, right above the text box that you are typing in there is a box that says Img and if you click on that, you'll get your image brackets. (See the Img box between the * and URL boxes?) Right between there you will insert your URL where you keep your photos online (I use flickr).
So, I go to Flickr, right click on the image and then select properties, which will pull up a window that shows the URL address. Highlight it, copy it, come here, open a new post, click on the Img box above, and paste the URL from wherever you have your pictures between the Img brackets. At least, that is how I do it. I also maintain my folks' website, and I can do the same thing from their page - just right click any image, highlight the URL properties and paste them here between the img brackets.