WordPress.org

I don't have any currencies in the drop downs

Check your currency lists have data in them in the WP Currency Converter settings page found at Settings -> WP Currency Converter.

Make sure you use the three letter currency acronym as per the ISO 4217 standard

This plugin uses Google for it's calculations so ensure the currency is one they support.

Can I add more currencies?

You can add any currency by it's currency acronym as long as it's in the ISO 4217 standard list.