You have to change the "default" font which isn't all that hard. Open a document, go the the home tab and select the little box with the down arrow under the "font" section (it is in the bottom right of the section). Select the little box/arrow and this will open the font selection box, change to times new roman with whatever size that you want and select the "set as default" button on the bottom left. You will get a selection box that asks if you want to apply your new font to this document or to all new documents. Select all new documents. When you open a new document, you will have the font that you want.

Hope this helped.