Do you mean Mining?
>To mine, the player must find a spot where the wall 'pings' by touching the screen and looking for sparkles. These spots will appear randomly in the Underground, usually in clusters, and can be located by looking for sparkles marked on the radar screen.
The player digs into the wall with a pick, which chips away small areas of rock, and a hammer, which breaks a larger area of the rock. Each spot will hide one to four items, including spheres, Fossils, Revives, Heart Scales, shards, evolutionary stones, Plates, and a few held items. -Bulbapedia
Anyway basically you need a pick and look for sparkly areas, and that's where you'll find items.