After a couple days after you can go to luminous springs, you'll have the spinda cafe announce to go to sky peak, then after that, corpish will be outside spinda cafe, and at the end of the dungeon he mentions, you get the manaphy egg, now to be sure to keep 2 blue gummis before hand or it will be very tricky! Give him the 2 blue gummis, then after while, he gets sick, and chatot tells you to go to a place, go there and get the Phione Dew to cure manaphy, then manaphy has to go back into the sea, then you have to go to Ageis cave with team charm, then after that, you see darkrai escaping cresila, then after a couple days after that, you have to fight darkrai and after you beat darkrai manaphy joins you and then a couple days AFTER that, manaphy tells you about the marine resort, thats when you can evolve your starters!
One of the reasons I liked the first PMDgame better is this.... This is SO complicated, and you pretty much have to do nearly everything in the game to do it... so when you finally evolve, there's not much left to do anyway... Don't get me wrong, though. this game is still awesome!