[Exim] Aliases

Sorry for my english but I really need help.

Hi, I try to use aliases and I can't, why?

With sendmail there's a file "virtusertable" containing the aliases like
that :

toto@???    user
titi@???    user

How can I use it with Exim? And how do I have to configure Exim?

Thanks for help.
Christophe.