Synthesized answer
The author, Austin Kleon, provides evidence in the form of his own experience and observations. He was asked to speak to students at Broome Community College in 2011, and based on this experience, he created a list of ten things he wished he had known at their age [1]. These ten principles, including "Steal like an artist" and "Don't wait until you know who you are to start making things," formed the basis of his speech [1]. After delivering the speech, he posted the text and slides to his blog, where it became popular and went viral [1].
Kleon then expanded this original manifesto into an illustrated guide. The book is described as including illustrative anecdotes and mini-exercise sections that prompt readers to take practical actions to foster their creativity [1]. The passages do not provide specific details of these anecdotes or exercises, nor do they offer further external evidence beyond Kleon's own reflections and the reception of his blog post.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Steal like an artist by Austin Kleon Description: When asked to talk to students at Broome Community College in upstate New York in the spring of 2011, Austin Kleon wrote a simple list often things he wished he'd heard when he was their age: 'Steal like an artist; Don't wait until you know who you are to start making things; Write the book you want to read; Use your hands; Side projects are important; Do good work and put it where people can see it; Geography is no longer our master; Be nice (the world is a small town.); Be boring (it's the only way to get work done.); and, Creativity…