Setting Default Currency and Multi-Currency Options
You can set the default currency of your shop from the admin section of the platform.
Head to the Settings > Currencies:
The Default Currency will amend the currency shown on your shop front.
Multi Currency Options
If you want the option to show your customers the price of your products in their local currency you can activate this through the multi-currency options. The rates are updated daily from OpenExchangeRates.Org.
Simply select the currency that you would like to show on the shop front from the list available. This will then add the drop down selection box on your shop front.