Tu parles français? Sprechen Sie Deutsch? Voce fala portugues? If you can speak another language, it can really help to make your profile stand out with certain employers.
Simply tap on the profile tab in the bottom-right of your app and select the arrow next to 'Language skills'.
Then it's just a case of selecting the language you want to add from the drop-down, before selecting your Spoken and Written skill level.
Once you've selected the levels, all that's left to do is tap 'Add Language' and just like that, it'll be added to your account.