Actually there's an available video tutorial in YouTube.
Refer to this link ---> YouTube - Spark Plug Replacement
Or you can type "spark plug" then you can choose from various videos.
Changing the spark plugs in our little zukis is a bit difficult compared to
that of cars with 90 deg. (perpendicular to ground) arrangement of
plugs. Ours is slightly tilted & the space is too small it limits your
movement. Unlike cars where you just pop the hood & the engine
is there. For pick-up type you have it under the driver seat. In my
case (van type), it's rear mounted.
There is a special tool called "spark plug wrench". I strongly suggest you
buy the one with the rubber inside. This rubber will grip your spark plug
& will not drop it upon installing it back. Mine does not have the rubber
so i'm more careful in installing my plugs.
I counted mine to be 24 half turns or 12 full turns (from full tight)
before you can successfully remove the plug.
Make sure you have the right specs & gap. Check your old plugs
for oil & black soot.
Hope this helps.