On a 4 cylinder, you have 2 wires and 4 plugs. The coil has an extender that goes deep into the cylinder, the wire is attached to the side to fire the 2nd cylinder. This is what is known as the waste-spark system.
To change the plugs, remove the black cover. Next, separate the wire from the coil. Then lift the coil straight-up out of the engine... you will see one plug hidden under there. Lastly, remove the wire and you will see the other plug. Since you have two coils, you will have two hidden plugs, the other two are under the wires.
Since it is a deep drop to the plug hole, replace the plugs by putting a hose over the white part of the plug and gently drop them down into the plug hole. You can also tighten the plugs since the hose will probably have a snug fit.
Since you have aluminum heads, be sure to dab some oil from the dipstick onto the threads of the spark plugs... this will prevent them from sticking inside the head the next time you remove them which saves the threads from being torn out.