Thanks all! I looked around before but couldn't find instructions. The directions are for adding a photo to a sig. I just want to add a photo to a thread. There's a really great thread about kids asleep at WDW, and I've got a good one.
The directions for adding a picture to your post are the same as those for adding an image to your signature until you get the the part about opening your User CP.
Instead of opening User CP, you will click the <Post Reply> button or the <New Thread> button.
When the text box opens up, type your message as you normally would. To add a picture, click the "postcard" icon located just above the text box.
A new box will open up where you can type or paste the URL of the picture on your hosting site in the box.
When you click <okay>, the code needed to put the picture in your post will appear in the text box. You can test to see whether the process worked by clicking on <Preview Post> instead of <Submit Reply>. This will allow you to further edit your post before it is submitted.