Take out the glove compartment (easy to do), and behind the glove compartment on the left, there should be a black box.
It may have a sticker on it that says Calsonic / Kansei. It may also have a sticker that has the following info (or similar):
FCC ID: CWTWC1U241
IC: 1788D-FWC1U241
P/N: TWC1U241
MADE IN MEXICO
CCAB06LP1410T1
Don't worry about the numbers, you're looking for a box with the FCC ID on it - that's the remote module. IF YOU HAVE THIS, then buy your remote key fob and we'll show you how to program it so that you'll have keyless entry.
Here's the steps to take:
http://www.nicoclub.com/FSM/versa/2011/BL.pdf