Type in this
and replace the word "link" with a direct link to the image you want to post, make sure the link has a .png on the end. If it's not a direct image, right click the image and click "Open image in new tab." like this
To take a picture of something you want to show, I recommend http://getgreenshot.org/downloads/
as you can select area of your screen like this
and auto upload to imgur.com (the best image hosting site) like this
and then just use the imgur link it gives you in the "link" spot.
I'm really hoping I didn't mess up the formatting of this post, it looks like this by the way.