Promo codes can be entered at the end of any claim filing process. Click the orange + button on the dashboard and go through the claim filing screens. You'll end up at the "Review and Submit" screen where you will see where you enter any promo code you may have. (I've attached a screenshot)
You can also enter a promo code via the app Settings. If you'd like to do that, here's how:
From the main dashboard tap on the PROFILE icon which is at the lower right -hand corner.
Next tap on SETTINGS.
At the top of the screen tap on SUBSCRIPTION then tap on I HAVE A SUBSCRIPTION/PROMO CODE
Enter your promo code and tap DONE
You can then go back to dashboard to start filing your next claim!