Probably the easiest thing to do is to just use the photo gallery on this site...
http://www.corvetteflorida.com/photopost/
Click on the link to Upload Photos and fill in the blanks. This will pull the photos directly from your own computer.
Once you do that, there is a section underneath of your photo in the gallery that says "UBBCode:" with a URL to the right of it. Simply click on the button to the right of that URL that says "copy to clipboard", then in any message you post, simply use the control-v function from your keyboard to insert that image into your posts. Or you can use the Paste menu option from your menu bar in the Edit section of your browser.
Pretty easy to do once you try it once or twice.