This is a method using a very handy tool which uses imgur.
Download and install the application:
imgur uploaderAfter installation, when right-clicking a previously saved image (in our case, screenshot) you can select 'send to Imgur' from the context menu.
Then under 'choose a format', select 'Message Board Lines', and then click 'copy upload information to clipboard'.
Paste that link in your post and you're done.
edit:There have been reports that this tool is not working correctly anymore.
Also it has not been maintained or updated for a long time now, so I thought to post a short tutorial on how to use ShareX as a very good alternative:
http://getmusicbee.com/forum/index.php?topic=18094.0