how do i change the spark plugs

Get some experienced help or take it to a mechanic. You do not have the knowledge or experience to do this yourself.

Do them one at a time. Unplug the coil and then remove the coil by removing the bolt that holds it on. Remove the spark plugs and install new ones with anti-seize on the threads. Use dielectric grease on the coil boot rubber mating surfaces to seal out moisture, install coil, re-install the small bolt and plug the coil in.

Bob is right that this is a job for an experienced mechanic.

Using penetrating oil on the plugs before removing may be a good idea and can help avoid stripping the threads. Soak over night for best results.