Good morning Margaret! My name is Alison. I am a computer professional with over 15 years of experience with both Mac and Windows. I'm sorry that you're having this issue. It would be my pleasure to help you resolve this.
To remove the ads, you will need to login to http://www.amazon.com/myk, then Click on the Devices tab, then click the Unsubscribe link by your Kindle Fire device. Please note: There may be a $15 fee to unsubscribe if you purchased one of the lower priced Kindles with ads bundled in. You'll be alerted if there is and given the chance to accept or to cancel.
If you want to increase the font size in a book while you are reading, tap the center of a page while you're reading. Tap the Text icon. Tap a font size option to make the text larger or smaller.
TO CHANGE FONT SIZES EVERYWHERE:
Your Kindle Fire or Fire tablet uses by default a text size of "1". While you can increase or decrease the text size, this won't affect the size of icons. To increase the text size on your Fire, swipe your finger down from the top of the screen, where the clock is, and tap on the Settings button on the right. In the list of Settings, tap on the "Display & Sounds" options. The bottom of that next screen includes a toggle, whose default value is "1". Tap once on the plus sign to increase text size: See if you like it: if you want your text even bigger, hit the plus sign button once more - 3 is the largest size. Note that this option increases the text size of everything that is part of your Kindle Fire tablet or Fire phone, which means that you'll see less things on the display, since they all take up more room. By the way, this text setting doesn't affect web pages - only the Silk browser's font size in the address bar and tabs.