There are a couple of ways to do this:

1. Get a photobucket account. Upload your pictures to your account. Underneath the picture you'll see some options on how to copy your photo. Choose the one with the IMG tag in front of it and then paste it to your post. Or you can click on the image box above the text input screen and paste it there.

2. If you don't want to get a photobucket account, you can host an image by clicking on the host an image button. Just enter the information in the box and it will upload your image. Then you can post your picture here using the directions from step one.