You should create a cover for your story, try asking for any artist’s help! And upload it as a background!!
Now coming to the text overlay, you’ll need some text overlay websites (I’m sorry, I will see of I can help you with any website) Upload the overlay in the overlays category.
Now sink both of them into once scene, you can check out some tutorials about how to use overlays and all. Finally you can see the results!!! If you need any further more guidance, you can ask me 
All the best 