In order to connect to an IRC server (which is, at the same time, part of an IRC network) using mIRC, you should type
/server any.servernamegoes.here, or choose one of the many servers from a list included with mIRC and that can be displayed by pressing Alt+E
To join a channel, you need to be connected to an IRC network/server. Once you've done this, type
/join #channelname.
Nickserv is a service that allows you to register (among other things) your nickname, so it can only be used by you. That's why you used to type your password
Hope that helps.
In peace and good thoughts,
/me
P.S.: Sorry about my English... not my first language, you know?
