Creating public static class

Hello,
I'm beginner in c#, but i have 7 years experience in VB6.
I just stuck with creating public static class.
my steps is:
1.creating new winform project
2.adding from solution explorer new class
3.changing type of class from "public Class1" to "public static Class1"
4.got an error "The modifier 'static' is not valid for this item"
what can i do?

thanks