Pokemon diamond help?

okk soo i'm stuck in diamond i am at the part where i just freed the pokemons (3) from team galactic . and i have to go to mt.coronet to see what their boss is up to, but i don't know how to get to the peak , one guy is block one entrance , saying something about him not having any pokemon , and the other paths don't lead me to the peak, where should i go ? i entered from heartome city in the cave, so i know i am on the right path.