You can normally do this through the gui tool, but I figured it's still fairly easy to do it with the command line tool. In this case, I want to join my machine to the domain and use Active Directory for authentication and user information. You'll likely want to back up your authentication config files (just backup /etc to be safe, unless you know exactly which files you need) before you start. Do this at your own risk.
system-config-authentication --smbrealm=my_ads_fqdn \
--winbindjoin=domain_admin_username --smbsecurity=ads \
--enablewinbindusedefaultdomain --enablekrb5 --enablewinbind \
If you want the users to have a default shell, run system-config-authentication again:
system-config-authentication --winbindtemplateshell=/bin/bash --update
Conversely, you could have added the "--winbindtemplateshell=/bin/bash" to the first command above.