When summarizing a text, read the text carefully, highlight the main points, and outline/lay out the writer's argument or stance to your audience.
The Declaration of Independence was created by the founding fathers of the United States. Within the Declaration, they explained their reasons for wanting to become independent from the British Empire. They include reasons such as being ignored when trying to communicate peacefully, failing to protect the founders and their rights, and rejecting their petitions. The founders assert that all men have rights and it is their right to declare independence.
The main idea of the text is that the Declaration of Independence was created by the people- and to protect the people- from the British Empire who they felt were not protecting their rights and needs.