You can read it here. It is short and straightforward. The main parts:

... Congress approves and supports the determination of the President, as Commander in Chief, to take all necessary measures to repel any armed attack against the forces of the United States and to prevent further aggression. ...

... the United States is, therefore, prepared, as the President determines, to take all necessary steps, including the use of armed force, to assist any member or protocol state of the Southeast Asia Collective Defense Treaty requesting assistance in defense of its freedom.

This resolution shall expire when the President shall determine that the peace and security of the area is reasonably assured by international conditions created by action of the United Nations or otherwise, except that it may be terminated earlier by concurrent resolution of the Congress.

In other words, the President is authorized to use military force in Vietnam without a formal declaration of war, he has that authorization until it becomes peaceful again unless Congress decides to revoke it.