Here you can find the instructions on how to set default language (store view) and currency.
Change the default language (store view)
Log into your Magento admin and go to the System > Manage Stores section.
Open the Main Website Store to edit .
Select a needed language (store view) from the Default Store View option dropdown.
Note, you should have at least two store views. Each store view should be a different language variant of your webstore. (E.g. store view 1 — your store in English; and store view 2 — your store in Spanish).
Click on the Save Store button.
Now you will see the specified language (store view) each time you store website is loaded.
Change the default currency
Go to the System > Configuration > Currency Setup section.
Select the needed currency from the Base Currency option dropdown.
Next you should set the same currency for the Default Display Currency and Allowed Currencies options.
Click Save Config button.
You may need to clear the Magento cache.
