In order for language and currency selectors to display on the frontend, you first need to sell with multiple currencies to multiple regions around the world.
To add currencies to your stores, please follow the guide here.
To add languages to your stores, please go to Settings > Languages > Add language and choose the language you want to add. Please bear in mind that you will need to install the Geolocation app by default for the languages to be added.
After finish the 2 steps above, the language and currency selectors should show up on Header/Footer section of your theme. If not, kindly contact us to be receive support.