If your SharePoint lists or libraries are set to track versions, you can restore a previous version of a list item or file. To learn how you can delete a version, all versions, or just minor versions of an item or file if your list or library is configured for it see Delete a previous version on an item or file in SharePoint. To turn versioning on, see Turn on version history in SharePoint.
Updated November 21, 2016 thanks to customer feedback.
Restore a previous version in SharePoint
Open the list or library from the Quick Launch bar.
If the name of your list or library does not appear, click Site contents or View All Site Content, and then click the name of your list or library.
Right click on the space between the item or document name and date, and then click Version History from the menu. You might need to scroll the menu to see Version History.
If you don't see Version History, click the ellipse (...) in the dialog and then click Version History.
You'll see a list of versions of the file.
In the Version History dialog, hover next to the version you want and click the down arrow on the right side to get a list of options.
Click Restore.
Click OK to restore the current version as the latest.
Note: SharePoint doesn't remove the earlier version you just restored, it creates a copy and makes it the latest version.
Turn on Version History in SharePoint
Version History is turned on by default in SharePoint, but if you don't see the Version History command, version history may be turned off. Depending on how your administrator has set up SharePoint, you may be able to turn on list or library versioning.
For information about SharePoint versioning settings, see Enable and configure versioning for a list or library.
Also see How does versioning work in a list or library?.
Not sure which version you have? See Which version of SharePoint am I using?