Follow the steps to create a new Transaction in the usual manner.
In Artsystems Pro, Fixed Currency Rates are saved in the database. Fixed Currency Rates may be updated in the Works Module>Edit Related Lists>Currencies. You may also select the most recent rate published by Reuters (http://www.reuters.com/finance/currencies) with a simple right-click in the Currency Rate field and choose to Refresh from Web.
NOTE: The Currency Rate on the Transaction is editable, so the rate may also be manually adjusted if needed.