I need to know every detail about it. Where to get the stamps from? How many stamps do i need? What kind of stamps are needed?How much will it cost me? How to send it? How long will it take to reach?
Stamps can be purchased pretty much anywhere in Singapore: SingPost offices, obviously, but also "S.A.M." machines found at all larger MRT stations, most convenience stores and newsagents, and most souvenir shops that sells postcards, although possibly at a small premium. Even Changi Airport has a post office in Terminal 2.
A regular postcard from Singapore to anywhere in the world including India costs S$0.60, except Malaysia and Brunei, which are just S$0.40. Stamps are available for the exact price, or you can use two local mail stamps at S$0.30 each, equaling exactly S$0.60.
To mail your postcard, drop it in the "Overseas" slots of a SingPost posting box, which are even more ubiquitous: you've virtually guaranteed to find one outside an MRT station exit, and of course at a post office or next to a SAM machine. Your card should reach India in 5-10 days, although what happens at the Indian end is another story...