First mark some text as Heading 1 style, then insert header. Insert Field with StyleRef Heading 1 then click OK. This good when you writing a book and you want to show the current chapter for each page.
Step 1: Type some heading words and select them.
Step 2: Click Home tab > Mark as Heading 1 style.
Step 3: Click the Insert tab > Header > Select Type.
Step 4: In the Design tab > click Quick Parts > Field.
Step 5: Select Links and References > StyleRef > Heading 1 > click OK.