Edit login module

I need to change the formatting of the login module.
In particular I need to fix the text, spaces or SIZES input text etc...
but I can not find the css to do this that should be the same template.
By inspecting the code I noticed that the associated class is "lbl-username" and "password-lbl" in class "login-fields", could not find any reference to these elements.
How can I change them?

Enclosed is the form that I need to change

Thanks to the support

Just add your definitions at bottom of template_css.css , there they will take advantage.