Using Gallery Forums are just like using any other forums... However, you can post images too!
After you create your post (subject and post, both required) you can click on the "Image Manager" link.
Adding images are as easy as:
1. Click "Browse" and a navigation area will appear that shows your computers files, navigate around to locate the image you'd like to upload. Once located, click on the image and select "open"; you can also choose to add a description (note that in v7.2 you do not have the option to change the description once another image is added).
2. If you wish to add another image, repeat step one; otherwise, select "done".
From here, just press submit, and your new "Gallery Posting" should appear for users to comment on your image(s).
I found it in FAQ
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