Export a Label file:
Open AOT, Expend Label node. Choose Label and require language to export. You can do it for individual language or you can select multiple language all in once.
Exported file will save on selected path with extension “.ald”.
Import Label File:
Right click on Label node in AOT and select “Create from File”, choose ald file to import than hit create.
Update a Label file:
Import the new updated label file system will ask to overwrite , go ahead
It will update your existing Label file.
Note: You must run full Synch after every import/Update.
More info: https://technet.microsoft.com/en-us/library/gg731886.aspx