Not too difficult, but a plan and attention to detail is required.. mock up the stripes.
Look at the door handle area of several cars with stripes; this area is the biggest problem area. If I recall, the door handles should be removed. The decal has a door handle cut out and you need the decal to be low enough on the door to hide the upper corners of the cut out... you will see this when you mock it up.
Anyway, do the door first. Get the area around the handle correct and the stripe straight/parallel/level/even (whatever you call it) with the body line going forward to match up with where the front fender decal will be. A small piece of painters tape at the rear of the fender/door gap will help you line it up.
The front and rear decals have to line up with the door so the door has to be right. Put it on, step back and look at it, and begin squeezing out the application gel, don’t let it move out of position by the door handle. In fact I would start there and go forward.
The front and rear stripes will have to go where they have to go to line up, but this is pretty easy... also the stripes are a little long so the can wrap around the door gaps, so plan for that.