Well... How you do some of the easier challenges (Amature and Rising Star) is by looking at what you have to do. Like if you have to Do 3 finishers (a message at the bottom of the screen will say youve completed that challenge) or you have to tag your partner in 3 times and win the match (where a message dosn't come up till youve won the match) Just read carfully at what you have to do, make sure you know the match type and the rules and of course of what u have to do.
with the harder challengers (Superstar and Legend) when u press X to get more info on the challenge you will be given an option to press start, press start and you get thrown into the match the challenge is asking you to do