If you want to do a clean install after the free windows 10 update all you need to do is follow this steps:
1. First click on the windows icon (In your case the taskbar should be at the bottom of your screen, I prefer mine on the left side)
2. Select Settings tool button
3. Then select Update & Security option:
4. In the last step select the Recovery tab and then click on Get Started option and you are all set to a fresh and clean windows 10 installation.