Will an entire model of my app, which includes every screen, assist me in the development process?

I created + designed every screen of my app on Adobe Illustrator using vector icons. I also had a iPhone template to mimic the resolution. I'm unsure whether this will help me in the long run, and how it specifically will. I'm new to creating apps but eager to learn.

Deciding how it should look is something you needed to do at some point anyway, right? It certainly can't hurt.