To insert a different header on the first page of a document than on the rest of the pages, activate the header section on the first page of the document. Double click near the top of the first page to do this.
Make sure that the header is active, you will see a Header & Footer Tools Ribbon Tab at the top of the screen. Select the check box for Different First Page. If you select this box when your First Page Header is active, you will then be able to put one header on the first page and a different header on all the subsequent pages.
You are done.