From UVA Writing Center

Setting Margins in Microsoft Word

Most word processing programs have wider margins than what's required.  To set 1-inch margins you'll need to adjust the software properties.

Open the program and click 'File'

Choose 'Page Setup'

The top and bottom margins are set at 1-inch, but the left and right margins are set at 1.25 inches each. These need to be changed, and the change needs to be made the default for all new documents.

Just change the margins by entering a 1 in the Left and Right margins. To make them the default for all new documents, click Default in the bottom-left.

You will be asked to confirm that you want to make the new settings the default settings. Choose Yes, and you'll be set.