Car will not turn off and key just spins in ignition

That sounds like the ignition switch actuator has failed. You can see the piece in the first image, it turns the rotor inside the switch to route power to the various systems as you move the key. They can break free and the key cylinder just spins. There is also a tab on the end of the ignition cylinder that engages the switch. To check or repair either one requires that you remove the entire switch to take it apart and see which is the case.
First thing is to remove the negative battery terminal to stop current flow.
Then you remove the key trim bezel and the center cluster trim (img2) then the trim strip between the door and instrument panel (img3) next remove the trim under the steering wheel (img4) then remove the metal support from under the steering column (img5).
Once you have those out you can remove the three bolts that hold the ignition switch assembly in the dash (imgs 6&7). You then pull the switch toward the front of the car and down to get it lower to get to the wiring. You will see a module and the switch that both have connectors. The module is the security module so gently remove it and then the wire connector on the ignition switch itself. Now you have the option of removing the switch and replacing it working under the dash, or you can press and release the interlock cable (img8) and pull the unit out so you can easily see what you are doing. Between the switch and the ignition housing you will see two clips, squeeze them and the switch will come free of the housing. To install a new one is to reverse the process, making sure the end of the cylinder and tab engage the switch and to re-seat the interlock cable fully.