1) Currency switcher is shown only on top bar, like you see in this demo variant http://floris.azelab.com/oddo/You should enable top bar in theme options at first.
Theme Options / Header / 
2) Then make sure currency switcher plugin is installed and activated. If for some reason you removed it, or it is not installed during the theme installation, you can add it anytime.
3) Make sure currency switcher widget was added in Appearance/Widgets
4) Make necessary settings - default currency, exchange rate, add new currencies etc in the plugin. Clikc "Settings" link under the plugin title.
Please note, if you want to use only one currency on your website, you don't need this plugin. Simply diactivate it, and set your default currency in WooCommerce Settings.
