Upload them to your photo gallery. Then click on the picture you want to display thats already in your photo gallery so it comes up...
1. Right Click on the picture.
2. Go to properties.
3. Highlight the Address (URL) and hit CTRL+C to copy the adress of the picture.
4. In your post click on the IMG button at the top and hit CTRL+V to paste the address you copied. and hit enter.
Thats all there is to it