There are various ways to unlock a locked document.
Right-click a locked document, (or a folder or the root node) and select the Unlock command.
Use the Delete tool in the List of Locks (see Managing document locks in the List of Locks):
Use the Unfreeze tool on the property sheet of a:
After check in using the option in the Check In Document and Check In Project windows (see Checking in Changes to Documents Stored in the Repository)
You must have locked the document or have the Full permission to unlock a document.