That would be "start the championship", that is, that team will be the first one to play.
I agree with Jackie, this phrase does not make sense translated literally into English. I think it would be better (in US English anyway) to talk about the opening round or start play.
Think about Wimbledon tennis guys. The commentary on the first day almost invariably commences with "Rafael Nadal, the winner last year, will open the championship on centre court in five minutes from now when he plays the unseeded South African Kevin Anderson in the first match of the tournament." In Portugal the phrase Nossa equipa would be used instead of Nosso time.
It makes perfect sense. The 'opening act' is the first act, the 'opening game' is the first game. 'Open' as in to 'be the initial participants in' is perfectly fine English.