Hello,
Step #1
Open up your existing language PO file with Poedit software.
Step #2
Go to Catalogand selectUpdate from POT file

Step #3
Then select the new xstore.pot file from latest theme update folder (xstore/languages).
Step #4 (OPTIONAL)
Next, you’ll see a mini box which includes all the new strings as well as obsolete string from the new POT file. Proceed by clicking the ok button.
Step #5
Once the import is completed, all the new string from the new PO file will be added and your existing (translated) string will remain intact as well.
Step #6
Finally, proceed to translate all the new string into your preferred language. Save. Move the updated .po and .mo language file back to wp-content/languages folder.
Regards