How to make the images pop up in window using Gallery2?

hi all,
Sorry about it to ask on Fedora mailling list. 
Anyway, could you help me? i am using Gallery2 and
i need the images to pop up and display in a window
when i click it, and the rest of the screen dimmed.
I see this in many gallery 2 sites. How to do?
Anyone can help?

thanks

regards,
Edwin Tan