Foreign Currency in Purchase order & invoice

I import some products from foreign market and sell it to local market. So I want to issue Purchase order & invoice in Foreign Currency and make the payment in foreign currency. Payment would be done in installments, so exchange rate would not be same.

Start by reading the guides
Set base currency | Manager
Use multiple currencies | Manager
Define foreign currencies | Manager

Setup your supplier to use a foreign currency
Enter suppliers | Manager

Will you be paying from a bank account in your currency or from a foreign currency bank account?
Record a payment | Manager

I Will pay from a bank account in my base currency