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
From the Quick Launch bar, open the list or library.
If the name of your list or library does not appear, select Site contents or View All Site Content, and then select the name of your list or library.
Right click on the space between the item or document name and date, and from the menu, select Version History. To see Version History, you may need to scroll the menu.
If you don't see Version History, in the dialog, select the ... (ellipses), and then select Version History.
A list of versions of the file appears.
In the Version History dialog, hover next to the version you want, and to get a list of options, on the right side, select the down arrow. Select Restore.
To restore the current version as the latest version, select OK.
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, it may be turned off. Depending on how your admin has set up SharePoint, you may be able to turn on list or library versioning.
For info about SharePoint versioning settings, see Enable and configure versioning for a list or library.
Not sure which version you have? See Which version of SharePoint am I using?