Even more basic is better, basically you could connect up your access controller to the key fob to toggle the lock / unlock. So a toggle button on the fob is a good option if it is a possibility.
You just need a spare fob and drop your 12V to the Fobs 3V
here is a great example
If you want to go direct to the central locking
If your manual doesnt have a wiring diagram, you might need top search for one online or pull the door card off to access the central locking module.
I would start by confirming blue/ green lock /unlock ( generally the wiring is the same , but not always ) you might see a pink wire or similar, that will do something like just unlock the drivers door.
Once you know what you are dealing with you can start building the solution, and what is going to be the best tool to achieve it, and xAC or Arduino etc
Once you have your car unlocked, do you plan on using a key to start? or installing a Push to start?