1. Find a Pokémon that can learn Strength:
* Machop can be found in the Valley Windworks (Route 209), or you can get one from the Pokémon Ranger, who will give you one after you complete the "Pokémon Ranger" side quest.
* Geodude can be found in the Great Marsh (Route 211).
2. Level up your Pokémon: You need to level your chosen Pokémon up to at least level 13 to learn Strength.
3. Teach Strength: Once your Pokémon is level 13 or higher, talk to the Move Tutor in the Pokémon Trainer's School in Hearthome City to teach your Pokémon Strength.
4. Use Strength: Now you can use Strength to push boulders out of the way and clear a path to climb muddy hills.
Important Note: You can only use Strength on boulders with the "Strength" symbol above them.