What does the declaration say people have the right to do if a government is destructive of their rights?

To alter or abolish it. Here is the full context:

That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness.