Hi Awais -
To add Reverb on an individual track you'd go to the Smart Controls panel ["B"] > Track tab, and under Plug-ins dial up the Master Reverb slider -- if you do that on only the Vocal Track you should only hear reverb on the voice.
If you do that and you still hear reverb on everything, then my guess would be that the mic may be picking up the track from your speakers and recording it along with the voice on the vocal track, so when you add reverb to the Vocal track it gets on everything. To test this, Solo the Vocal track [click the little headphone icon in that track header] -- if you still hear the other Instruments, then that's what's happened. If that's the case, when recording with a live mic, turn off your speakers and monitor in headphones instead.