What would she know about what to do with the power? She's just a child who doesn't know or understand what is needed and whats to be accomplished.
Its a pity that Cyclops didn't think of this before instead of just stubbornly labelling her the Mutant Messiah without explaining or thinking about what she was expected to do as a messiah.
It's rather ironic isn't it? Still, I think this is more of a power trip than anything. The way he was talking to her, it sounded like he's not interest in giving her the Phoenix nor even interested in restarting the mutant gene