Did you install pro and wanted home?
Do you have a win 10 installer? download the
Windows 10 media creation tool and use it to make a win 10 installer on USB, if you don't
Only way to get back to Home from Pro is a fresh install - its not that hard really and includes the wiping of the hdd in process.
change boot order in BIOS so USB is first, hdd second
boot from installer & follow this guide, its really helpful and shows a step by step approach with screen shots:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
When you reach screen asking for licence, click "I don't have a key" and win 10 will continue to install and reactivate once finished