Hello making a vb.net project for college course.

I have 2 forums
FORM1 = is a car sale forums helps company sells cars by doing calculations
FORM2 = is a login screen they need to log in so that they can use the car sales form (form1)


When they log in i want FORM2 the login screen to disappear and not stay at the back.


If the login is incorrect how can I display an error message?

Thanks all!