You can find the goals and powers in the Preamble.
A preamble is a preliminary statement or an introduction to a document.
In the Preamble to the U.S. Constitution the phrase 'We the people' establishes the fact that the government derives its power directly from the people of the nation.
The Preamble outlines six main goals, they are: to form a more perfect union, to establish justice, to ensure domestic tranquility, to provide for the common defense, to promote the general welfare and to secure the blessings for liberty.