When any published item is edited or being edited, the item is placed in a status of checked out which makes it editable only by the authorized user who created or edited the item. This is clearly define with an icon graphic of a padlock.
To make the item editable, simply click the padlock icon.
To check-in all the locked items on the current page
Select all the items with padlock icon and click Check-In button at the top
To globally check-in all items
Go System > Check-In
Select all items in the list and click Check In button