You want to accept currency other than US dollars, the system default.
From your Admin Area, click on Tools -> Payment Settings and enter the exact ISO Currency Code for the currency that you wish to accept. The most common codes are USD (for American dollars) and CAD (for Canadian dollars). The list of ISO Currency Codes is here.
NOTE: While your system will display any currency code entered here, you will also need to be sure that your payment processor processes payments in this currency.