When you log out from the app, you will be suggested to create a Face ID to log in easier into the app next time. So when you open the app next time (after you create a Face ID) you will be able to log in with a Face ID option. If, due to some reasons, you do not want to log in with Face ID, press “Other options”, - you will be suggested to log in as usual. 

The account itself still needs to be created with an Apple ID/ phone number/ email/ Snapchat/ Facebook.