I am searching for,where to install login screen package,and make changes in it.i searched for login manager in system,but cant find it there.
i am using gnome.
With gdmsetup (run this as root) you can change the login screen and some other settings for sessions and login.
Gnome Art is a good place to start GNOME Art - Login Manager
Many login themes will work by downloading the login theme, and then just drag it into the gdmsetup screen (set it to the local tab).
Haven’t done much with this myself but as I hear some themes don’t come out as nice as you hope, so test with a couple until you find what suits you 
Cheers,
Wj
Thanks,its works as follow your post.