Process by on "Fable of the User Centered Designer"

Hello I just finished reading the short ebook in the udemy course Ultimate Guide to UX : https://www.udemy.com/ultimate-guide-to-ux/. These are my notes, can you explain to me how this process takes in the real world? For example, you’re the UX Designer, and your web application is maybe like Facebook/Twitter, how do you go through these stages?

[B]PROCESS in the book

EARLY AND CONTINUAL FOCUS ON USERS AND THEIR TASKS[/B]
Talk about your customers.
Determine who are your customers.
Determine how they use your software.
Develop persona based on research findings.
Developer red routes still vague
Red routes - process in your system that needs to be smooth

[B]EMPIRICAL MEASUREMENT OF USER BEHAVIOUR[/B]
Setup usability test
Find out how people use your products.
Watch how they navigate on your system.
Measure the usability via red routes
Usability measurements:
Effectiveness
Efficiency
Satisfaction

[B]ITERATIVE DESIGN[/B]
Build paper prototypes
Let the customer test the system with just prototypes
Design multiple prototypes and pick the best and improve upon it

Hey AJ,
Great question. Are there any of these steps that you are specifically unsure of?