Choosing a currency on eOrder is automatic. 

If you are from the United States - It's going to be: (Numbers) of $$ American Dollar.

If you are from Euro zone - it's going to be:Euro.

if you are from England - it's going to be: Pound Sterling.

When you create your products and set a price, this is going to be a currency for your accounting office.

As soon as your sales rep is making an order, all transaction goes through in a currency that you are working with.