In order to configure Multi-Currency in Magento 2 please go to Admin Panel > Stores > Configuration > General > Currency Setup.
To set up the Currency Options expand the section you see below.
1. Set the Base Currency the prices in the 'Admin Panel' are set in.
2. In order to choose the currency which will be shown to the customer by default, set the Default Display Currency. To be able to display currency based on customer Geo location use Auto Currency Switcher Extension.
3. The Allowed Currencies enables you to choose currencies that will be available to a customer on a Storefront.
Once you have finished with the Currency Configurations press the Save Config button.
Read more about Currency Rates Configurations.