How to Fix/Change Ignition Barrel? 1998 (R reg) Ford Mondeo LX Estate, 2L, ?

Someone tried to pinch my car and wrecked the ignition barrel, I have bought a new one but Im unsure how to fit it? and as the car has an immobiliser will the new barrel work at all?
The new barrel has the same number and a 2 button remote key.
Any ideas, thanks Noel