This is the "in-depth" version Brian, most of which I'm sure you already know, but I just cut and pasted it from another thread, so bare with me...
1. Find a picture you dig.
2. Right click on it, and you'll see a URL listed in the large box that pops up.
3. Highlight that URL and copy it (Ctrl-C)
4. Then go to the spot in you post where you want the picture placed, and hit this button
(from all those buttons you see above whenever you're posting something)
5. Then paste (Ctrl-V) your link that you just copied right in the middle of
these two sets of brackets
that you should see.
That should be it. Hopefully that's not too confusing. If it doesn't work for some reason, give us a holler, and we'll take a crack at a another tuturial. If you just take it a step at a time, it should work fine. Give it a shot and we'll see how it works! Good luck!