Setting your base currency
Your base currency is the one everything is reported in. Set it once in Settings.
Your base currency is the single currency your dashboard reports in: income, expenses, profit and loss, and runway are all shown in it.
Setting it
Open Settings and choose your base currency (ISO code, for example USD, EUR, GBP). The default is USD. Pick the currency you actually think in and file taxes in.
Changing your base currency re-expresses your totals in the new currency using historical rates, so your history stays consistent.