Find the image on the web you wish to post. Right click on the image, scroll down the list and click on "properties." In the box that opens up, highlight the address next to "Address (URL)", then press CTRL+c to copy the URL.
In your reply, type <img src=" then press CTRL+v to paste the URL you copied earlier, then type ">
It will look like this:
<img src="http://boardingarea.com/blogs/deltapoints/files/2012/07/test.jpg">
Thank you kindly!