1. Visit http://www.mozilla.org/en-US/
2. Right-click anywhere on the page
3. Select "Save Page As..."
4. Enter your desired file name and save it to your computer!
5. When you want it, just open your file explorer and then click on the file.
If you just want to save a screenshot, press Shift+PrintScreen, then paste it into Paint or whatever you're using. Best wishes!