How do you get into galactic warehouse

It is in a town where the fighting type gym leader is. You have to defeat a the gym leader in area. The last gym leader you face is the water type one. the glactic guy will be there then you battle him. Next you do the thing in the mountains in the center of the map. Then you beat the galatic boss in the mountains. lastly you can go in the galatic warehouse and you can also go in the on other bilding there. You can go there the first time after you beat the gym leader there, but I like doing it that way.