How can I fix my Nissan Almera?

My son accidently left my car lights on. 5 hours later, I found that the car wouldnt start and appeared to have no power at all so I left it for an hour and tried to Jump start it from a friends car. We did everything correctly i.e. possitive to possitive etc. Now the car central locking makes a noise when you try to turn it on and a tick tick type of sound but we still cant seem to start the engine. The Radio, washers, and windows all work now but they didnt before. What can I do to fix the problem? It is the battery that needs replacing or do I new to sort out the imoboliser? Please help as I have no clue about cars. Many thanks