Please use the free image hosting service to upload images.
Once you click "host it" a new page will open which will contain links you can copy and paste into your gl5 Post to display the image. Please note images may take a minute or two to upload, therefore the new page may take a while to display.
For example this a link copy and pasted for the "Thumbnail for foums (0)" option. Which has link to the main image too rather than displaying the whole image in the Forum.