set web site URl to show virtual directory

Hi ,
I am newbie on this forum, sorry if this question was
posted.
I have a website called A and under it a virtual directory called
B.
I set a url domain.com on web site A. So I have the IIS welcome page
When calling domain. com
If I tape domain. com/B I have the content of my virtual web
I need to show this by just calling domain. com and not domain. com/B
( easy for people)
How can make this redirection ?

Thanks very much