So far, the font sizing advice has been limited to the web browser. If the you are interested in increasing the size of all text within the Win8.1 environment:
1. Right-click on your desktop background and select "Screen Resolution" from the menu.
2. Click on the link that reads "Make text and other items larger or smaller" which is located below the other display settings (2nd from the bottom on mine).
3. Slide the sizing slider-bar towards "Larger" and click the "Apply" button.
Another option would be to reduce the screen resolution on that first window. That may or may not work well depending on your monitor's compatibility with the lower resolution. Think of it this way, lower resolution (less pixels) distributed across the same physical screen surface area equates to the pixels needing to be larger. Everything "appears" larger that way. However, the LCD display has a real number of physical pixels known as its native resolution. So, faking other resolutions by having the LCD emulate larger pixels can sometimes look soft and fuzzy.