how do i light up background?
 

i shot a picture on a balcony at night with a very pretty lit up church in the background. i had to use flash to lite up the couple but the church was dark.i used 2nd curtain sync but the church was stll dark.what should i have done?

Expose for the church, probably using M (Manual exposure) mode, but use SLOW sync for the flash. This will hold the shutter speed to what you want otherwise the camera may switch it to 1/60 second for example. Your camera may combine slow sync and second curtain, investigate in the user manual.

Second curtain sync fires the flash as the shutter is about to close instead of when the shutter opens. Classic usage is a combined flash and time exposure of a moving car with the lights on. Normal sync will have the light trails ahead of the flashed car image while second curtain will show the light trails properly after the flashed car.