To add more currencies, click on button "Select" at the bottom. Then select a broker feed from top left corner of the "Securities" window that will open up. After that select currency you want to add and click "OK" at the bottom of the window.
In case you want to select more than once currency pair, then press and hold "Ctrl" button on the keyboard while selecting with the mouse different currency pairs. Click "OK" to add all selected currency pairs in the "Streaming Quotes".