[DaveR]

I have a car question and admit that I know absolutely nothing about cars!   

I have a 2009 Honda Fit.  Last week my car would not start.  Called road service and got a battery jump and then took it to my local mechanic to find out what happened. The car battery is only a year old.  I was told that the overhead light had been left on.  Not sure how that happened but I was told the car is fine.  

But now my key fob isn't working.  I can start the car after I manually open the door, but it's a bother!  Does it also need a new battery?   Where do I take it to have the battery replaced?

Hi Debbie,,
As Don said.. your Key fob battery is meant to be replaced, and being that its 5y old..its probably time. 
If you look closely you’ll probably see a seam around the middle,, there may also be an indentation somewhere along that seam. Use a flat head screwdriver or maybe a Dime and pry it apart..GENTLY.  It should pop open..you should see a Battery, pay attention to which side is + and which is - before you remove it and then replace with a new one.  

Let us know how it goes.