They are threaded into the cylinder head. Your car has what is called Direct Ignition. This means that there is no Distributor Cap or Rotor. On your Engine, there is a separate Ignition Coil for each Spark Plug. So the Spark Plugs are under each one of these Ignition Coils which are on the Cylinder Head. There is an 8mm bolt that holds each one of the coils onto the Cylinder Head.
I hope that this is enough to help you. Best of Luck!