I don't think he means in photoshop. To make it brighter in camera without photoshop, make the shutter speed slower or make the aperture bigger if possible. Then you won't need such a high ISO also. Doesn't look like anything in the pic will be affected by slow shutter speed. Try several seconds.
Overall, interesting picture. Don't see such everyday. :thumbsup:
Edit: Did an example in photoshop, but this is achievable with camera only if you don't like photoshop. Will take down the pic if you'd rather.
tinkering the exposure in the ps like mr altered vision did to ur pics shows a marked improvements as ur new to photography keep shooting pics,learn some basic rules of composition,etc learn to understand that a pic is like a dialogue between the viewer and the photographer....shooting subjects that are popular with one and all ,nice way to begin learning photography......