Currently Smile is not yet translatable.
Once you are using a paid plan with Smile, you will be able to access editing the text within the Display section.
At a glance, here is some of the text that is editable:
Here are some examples of text fields in app that are not editable:
If you'd like to be added to the feature request list for translations, let us know at email@example.com and you can be notified when this feature becomes available.