once mIRC is open press ALT+O .. or click the 2nd icon from the left in the top icon bar
that is where almost all of the mIRC setings are stored. and you 'configure' it from there.
as for more specific information if you could re-state your post to be more specific and accurate i could explain where specific items u may want are located .. right now i'm not exactly sure what you mean
when you logon to a domain? does this mean connect to an ircserver ? or when u boot windows and u connect to a Network Domain ? .. please try to be very accurate with your wording. thanks