SharePoint Enable Audit Logs

Open SharePoint Power Shell, run following commands:

$site=Get-SPSite http://sitecollection

$site.Audit.AuditFlags = [Microsoft.SharePoint.SPAuditMaskType]::All

$site.Audit.Update();

SPAuditMaskType:

None	No events or actions.
CheckOut	Check out of the object.
CheckIn	Check in of the object.
View	Viewing of the object by a user.
Delete	Deletion of the object.
Update	Update of the object.
ProfileChange	Change of a profile.
ChildDelete	Deletion of one of the object's child objects.
SchemaChange	Change of the object's schema.
SecurityChange	Change in a security configuration for the object.
Undelete	Reversal of the deletion of the object.
Workflow	Use of the object in a workflow task.
Copy	Copying the object.
Move	Move of the object.
Search	Search of the object.
All	All types of events and actions.