how do i make users to login via email vs username

by default Dolphin allows users to login via email address in 7.1. Instead of logging in via username I want my users to login via email or fb connect on both iPhone and Android apps. How can I make this happen

Login via email (and user ID, I imagine) works in the mobile apps.  To change the text on the login page, you'll need to order a mobile license or Prime.  This nets you the source code for the mobile apps.

Have you tested this. no it doesn't work on my app...it ask for username. this is a bummer because we ask for our users to access the site via email

I'm only able to test on the Android app, but it should work the same way for iOS - if not, that's probably a bug.  The label says username, but inputting the email address should still work.

I've just checked it. I was able to login with email in iOS and Android apps.