Edition: Enterprise
User-level: Director, Assistant Administrator, System Administrator
You'll need to add the currency to your organisation before you can set up a project and invoice in a foreign currency. The steps below will walk you through this.
Organisation menu > Settings > Financial > Currency from the organisation dropdown menu
Select Add Currency
Select a currency from the dropdown menu that appears, you can also type in the country/country code
Select Save
Repeat this for all the currencies you plan to invoice in.