First step is to remove everything you need to access spark plugs. Sometimes nothing, usually tank and air claner box...So, let's remove tank.
And air box. You need to untighten clamp screws.
Remove spark plug cap (pull on it) on cylinder 1. Use spark plug wrench to remove spark plug.
Throw it to basket and take new one. I think it's better to put some high temperature grease on it, in order to not damage cylinder head.
Install spark plug in wrench. Be careful to not but spark plug directly in the engine, and especially not on the bad side. Start tightening with hands, and, if it seems too difficult to tighten too early, take care that it doesn't go wrong. Then finish using torque wrench.
Now you just have to do the same for others plugs, and, when it's over, reinstall everything and you're done.