On the desired budget, click Settings (1)
Switch to Currencies tab (2)
Here you can edit the exchange rates (3) or update them online (4).
The standard currency (5) sets the base for the exchange rate.
You can budget every account with any defined currency. (1)
The first Total column (2) always shows the amount in the account's currency. (2)
The second Total column (3) always shows the amount in the selected display currency. (4)
You can change the currency in which the sums are displayed from the bottom of every screen.
Switching this does not affect the actual budget.
For every printout, you can choose the currency without changes in the budget.
There's also an option to print the exchange rates as an annex.