By setting your header to be "first page only." It is a checkbox in the header/footer tools ribbon. Note that if you have multiple Sections, you need to make sure this setting is not repeated in subsequent Sections or that the link to previous setting is turned off. Word sometimes inserts Sections without telling you! "Section" is a word of art in MS Word, as is "template."

Sections / Headers and Footers in Microsoft Word 2007-2013