In administration panel go to Configuration => Configure modules
Select Currencies module
Currency will be set as active in a shop.
If you select a currency, Additional options will be automatically filled.
The current exchange rates http://nbp.pl/home.aspx?f=/kursy/kursya.html.
Currency will be set as default in a shop.
List of the codes compatible with ISO 4217 http://www.iso.org/iso/support/currency_codes_list-1.htm
If selected the foreign currencies are calculated with the inverse exchange rate.