Capturing ghosts? I'm guessing you're talking about the mansion quest, or the lost souls quest.
The mansion quest requires you to go around the bottom floor of the mansion looking for blue souls. If you find em, bring em back to the center of the map (where ya walked in) and talk to the blue spirit. From there, get four souls by giving money to the greedy spirit (direct left), acquiring hot spring water from the garden above the room (top left), gathering 5 herbs (top right) and finding the ghostly lotion (due right). Once you acquire these souls, go back to the center and tromp the boss enemy.
After the mansion is cleared of ghosts, go left, and talk to the woman with the spirits by her for the lost souls quest. Then go out into the world and find the silver chests that you've been seeing, but cannot open.
Hope this helps.