Well there is a sticky that somebody will probably lead you to.
But I can tell you how to also:
First off, do you have an online image hosting account i.e. photobucket...putfile...etc?? If not, you need one (www.photobucket.com it's free) & then you upload the image then copy/paste the image code - which looks like this:
- into your message and that's it! Would love to see some pics of Skittles!!