How do I modify a bread recipe to make softer fluffier bread?

You are using to much flour. You have to watch with bread/pizza dough recipes you don't always need to use as much flour as it calls for or sometimes you need alittle more. Make sure that you kneaed it for 10 - 15 minutes to get the yeast really working. You want to take a small piece of the dough and stretch it and hold it to the light to see if you can see through it - if not need some more. I also like to put mine in the fridge overnight and then let it sit for an hour before I use it.