You'll need a repair disc to boot your computer into the Windows Recovery Environment to restore the previous version. If you have previously created a full backup, you can now use it to go back to the previous version of the operating system. There are no excuses: No matter what, you should periodically make a full backup of your computer - you never know when it will come in handy. The Slightly Less Easy Way How to uninstall Windows 10 using the full backup option

In that case, you still have some choices: You can go back using a previous backup, or you can do a clean install of the operating system. If you don't see the option on the Settings app to go back to the previous version, you're either trying to uninstall Windows 10 after the first month you performed the upgrade or there is something else wrong with your computer.

If you need those settings or apps back, you'll have to go install them again. Keep in mind that uninstalling Windows 10 from your computer will remove apps and settings configured after the upgrade.

Windows 7 to windows 10