Here's the prominent section of the Declaration of Independence that expresses the idea of popular sovereignty. I've bolded the key points to that effect:
"Popular sovereignty" means the people are in charge of establishing a government over themselves. The founding fathers of the United States adopted the idea of popular sovereignty from Enlightenment philosophers like John Locke (of England) and Jean-Jacques Rousseau (of France). The Declaration of Independence (1776), written primarily by Thomas Jefferson, asserted the concept of popular sovereignty. The Declaration insisted that people institute governments in order to secure their rights, and that governments get their authority from the consent of the governed.