Support for multiple currency accounts is currently available for Xero and QuickBooks Online, but not yet FreeAgent.
Float will use the base currency from your accounting platform as the base currency for the cash flow. If you have any bank accounts in an alternate currency these are converted and displayed in Float using the base currency from your accounting platform.
Similarly any invoices or bills in an alternate currency will automatically be converted to the base currency ensuring that the cash flow is displayed in a single currency.
Clicking into an alternate currency invoice, bill, transaction etc will display the original currency data along with the exchange rate used for conversion.