How do you open the ancient picture in Pokemon Pearl?

You can't "open" the Ancient Picture in Pokemon Pearl. It's a key item that you need to take to the Lake Acuity area and show it to the spirit of Azelf, who is located at the top of the mountain.

Here's a breakdown of the steps:

1. Obtain the Ancient Picture: You get this item from Riley in Snowpoint City after defeating the Elite Four.

2. Travel to Lake Acuity: This is the northernmost area in the game. You'll need to use Surf to get there.

3. Reach the top of the mountain: You'll need to climb a long, winding path, battling trainers and traversing icy areas along the way.

4. Show the picture to Azelf's spirit: At the very top of the mountain, you'll find the spirit of Azelf. Show him the Ancient Picture to trigger a cutscene.

5. Capture Azelf: After the cutscene, Azelf will appear and you can try to catch it. It's a powerful Pokemon, so be prepared for a tough battle.

This process is crucial for completing the post-game content of Pokemon Pearl and obtaining a powerful Pokemon for your team.