Importing language package is one of the easiest way to have different language in your online store.
Make sure that you are in backoffice of your online store.
Click on Localization>Translation
Reach on “IMPORT A LANGUAGE PACK MANUALLY” form segment.
Now upload your design lanuage pack. Mostly language pack will be in .gzip. Choose the theme on which you are going to apply desire langauge pack
Click on Import button to finalize.