Chuck,
I'm not sure how picasa exactly works, but if you upload your photos to that site, or any site for that matter, just follow the steps below and you should be ok.
1. Once the pic is uploaded, right-click on it and go to "properties."
2. In the window that pops up, you shold see an "address" area, that gives a big long http:// address for your photo. Highlight that and copy the address down.
3. Come into the forum and paste it into the text window. Then, you have to type these tags
after. That begins the image and ends it.
It should look something like this
4. An alternate method is to press the "insert Image" button above (just below the itallics button) and it will put those tags in for you, then all you have to do is paste the photo address between.
Hope this helps!