This event fires when a new client (computer) appears on your network. Of course, client must be set for automatic network configuration. First thing you should do when this event fires is to select a free IP address that client can use. Selection of IP address is all up to you, so be careful not to use addresses that are already in use. After you select an address and put it in Session.IPAddress, you should specify Session.LeaseTime property. After that, you respond to the client by calling Session.SendOffer() method. Here's an example:

Private Sub DHCP_Announce(ByVal Session As wodDHCPServerLibCtl.IwodDHCPSession)

Session.IPAddress = "192.168.1.2"
Session.LeaseTime = 3600 ' 1 hour
Session.SendOffer

End Sub