You should be able to double click into the header and footer, and then delete all the text that is there. After you delete the text, you can also choose to adjust the margins for the document, so that there is more space at the top and bottom. To change the margin size in Word, go to the tab labeled "Page Format." Then select the "Margins" drop down box and select the desired settings.
You might also turn on the Show/hide button to see formatting. It looks like a backward P on the Home page. A page break might have been inadvertently added while you were typing.
