I have a lenovo y510p running windows 7. I need to restore to factory setting but I don't know how to?

Yes Throwing out the baby with the bathwater is what restoring to factory setting does. All your programs will be gone.
You can contact Lenovo about instructions or search Google.

Shows on the 1 minute mark of the video
Better is to clean up the computer--
Avast! Or AVG or Trend Micro House Call
Malwarebytes or Spybot
Disk clean up or Ccleaner
Eusing Free Registry Cleaner
Defragment.
All those have free versions, work well with most Windows.