For changing view, it is possible only if a cameraman start a multiview record, but noone should have this password as the cameraman would have direct retransmission of the match with no delay.
Else, it behave the same way as a normal game : you just click.
To change server type /gtv_watch x (where x is the game number). Anyway, a list of the servers and game to watch are shown when you enter the server if no game is currently watched by anyone, or directly you join the current match if there are people already watching it on GTV.
For ref, I will post the informations soon, I wait for Ghosty to apply a common setup.