Reset car key?

Hi, I have a S reg, 3door clio & the key button isnt workin the central lockin (all i can do 2 unlock doors, is with key in drivers door and lean over 2 open passages door) so I took it 2 halfords & they changed the batteries & said if its still not wokin, then I will have 2 reset key... Please please help me...HOW DO I GO ABOUT THIS, I was told it is something like turn the key 1 way a curtain amount of times etc