Instructions
Go to the Ruins of Alph just off Route 36, next to Violet City in the center of the Johto region. Go into the cave next to the research center and you will find a puzzle on the wall. Press A to start it.
Use the stylus on the lower screen of your DS to rotate and slide around the four moving tiles until you have made a picture of the Pokemon Kabuto. Completing this puzzle unlocks the Unown corresponding to the letters A through J in the Ruins for you to battle and catch. A scientist will come up and give you the Unown Report, which records which Unown you've caught.
Go to the cave to the south of the entrance to the Ruins. Use a Pokemon's "Surf" move to get across the patch of water leading to the door and head inside to find the puzzle. This time you have to rotate and slide seven moving tiles on the bottom of the screen to make a picture of Aerodactyl, a dragonlike Pokemon. This unlocks the Unown for the letters R through V.
Go to Union Cave, between Routes 32 and 33. Go down the ladder midway through the tunnel and use a Pokemon's Surf move to get to the exit at the north of the cave. Here you will find another puzzle, this one with 10 tiles you can slide and rotate on the bottom screen of the DS. Assemble a picture of the bird Pokemon Ho-Oh to unlock the Unown that look like the letters W through Z.
Go back through Union Cave. Instead of going through the exit at the north of the lower floor of the tunnel, head west and use a Pokemon's "Strength" move to shift the rock to get into the final cave. This one has nine tiles you can slide and rotate, and when assembled is a picture of Omanyte, a Pokemon that looks like a fossil. Complete it to unlock the Unown for the letters K through Q.