What do you mean by guild (theirs guilds for Magic?), anyhow the best advice I can give is do your best and don't over think it if you mess up or feel they saw something don't stop in your tracks , finish the trick, get to the finish line.
They give you a ward at the gates of the college, and the woman you talk to throws fireballs at you. Just equip the ward and a steel sword (you can find one in the bandit camp near winter hold.) after you defeat her, you'll be let into the college of winter hold and can join the mages guild!
But seriously, videogame references aside, just try your best, and have a plan B handy.