Here's how you can find and catch Articuno:
1. Obtain the National Pokédex: You need to have the National Pokédex to encounter Articuno. This is obtained by beating the Elite Four and becoming the Pokémon League Champion.
2. Travel to the Seafoam Islands: The Seafoam Islands are located to the north of the Kanto region.
3. Explore the Islands: Articuno will be found deep within the islands, so you'll have to explore them thoroughly.
4. Encounter Articuno: You'll encounter Articuno randomly as you explore the islands. It is likely to appear in the highest level areas of the islands.
5. Prepare for the battle: Articuno is a strong Pokémon, so be sure to bring along strong Pokémon and some healing items.
6. Catch Articuno: Use your best Poké Balls to try to catch Articuno. You may need to weaken it first before you can catch it.
Remember: You can only catch one Articuno per game, so choose your moment wisely!