you can try to override that using your theme style.css just simply use chrome or firebug to inspect elements and then used it’s css class or id name.
Hi,
I have a similar problem here, but I’m afraid I don’t know how to make the changes. My login box is too large, please see the following screenshot:
https://www.dropbox.com/s/4m37y9lrlwwkysp/screenshot_lwa.jpg
My knowledge about php is limited, and I can´t find where to change the lwa-username-input and lwa-password-input text box sizes.
Thanks a lot,
Daniel