The best practice is to use forex rates directly from you broker. It's very easy to export historical rates from MetaTrader to Forex Strategy Builder. Here you can register an extended FastBrokers demo account to do so. There are links to tutorials lower in the page.
Date Time Open High Low Close Volume 2009-11-17 14:50 1.5018 1.5021 1.5017 1.5017 293 2009-11-17 14:55 1.5017 1.5019 1.5016 1.5017 288 2009-11-17 15:00 1.5017 1.5024 1.5017 1.5024 331 2009-11-17 15:05 1.5024 1.5031 1.5024 1.5029 346 2009-11-17 15:10 1.5029 1.5029 1.5025 1.5025 239
More information about the integration of historical data in Forex Strategy Builder, the different data formats and data sources can be found in the support forum and in the following articles and tutorials: