You have a couple of options, you can upload your photographs from your hard drive into your Pixalo Gallery (see the guidelines for the "Members Gallery"
here), making sure your shotis within the size limits . Once you have done that, you will see underneath the photograph the code which you copy and paste into a text box here on the Forum.
Alternatively, you can use a link from another photo storage facility to show your image here (but please show the photo and don't just link offsite to it).
Hope that helps!