Okay so looking at your image, you successfully connected to the server. You're halfway there. Just close that mIRC favourites window and in the status window type in the following:
and you'll be in the chat room. I suppose entering "psypoke" into the box you were asking about and clicking join would work but I never bothered with that so I'm not sure.
And what it all comes down to
is that everything's gonna be quite alright