c# threading

I have three forms

form1:
this form contain a text box and a button

form2:
this form contain two webbrowser componets in two pannels

form3:
this form contain two webbrowser componets in two pannels

first form1 will appear and user will enter text in the textbox and will click the button

Can anyone tell how to start the other two forms(form2,form3) in two different async threads
after the button is clicked on form1