ok, file edits are done
go to your forum/ACP/"Posting" tab/"BBCodes" tab/ "Add a new BBCode" button
In the "BBCode usage" box, add
In the " HTML replacement " box, add
<span style="background-color: transparent;">
<a href="{URL}" rel="lightbox"><img src="{URL}" alt="{L_IMAGE}" width="300" /></a>
</span>
In the "Help line" box, add
enter the "URL" of the photo you wish to display
In the "Settings" section, check the box
"Display on posting page"