Calling a WINFORM from another WINFORM

I've been coding in C# for about one year now, but only have coded
ASP.NET, web services, single-form WIN apps and Compact Framework apps.
But I have never needed to worry about multiple WINFORMs being used by a
WIN app.

So how does one transfer control of the WIN application to another
WINFORM? 

For example, I have a WINFORM (Login window) that will authenticate a
user (using webservices) and if the user is authenticated, I want to
close the login WINFORM and call the WINFORM that handles the app.

Best Regards,
 
Darren Swartzendruber
darren.swartzendruber@xxxxxxxxxxxxxx
(864) 679-3485