In order to cast and use a variable as a class, you can either assign it to a variable that is of the class type, or call it in a method call with the name of the class as the instance, and by adding the variable to be cast as the first parameter:
euclass Something( atom s )
-- ...
end euclass
atom a
Something x
a = 5
x = a
x.Method()
Something.Method(a)