Instructions
Travel to Route 207 using your favorite mode of transportation. If you use your bike, you must dismount it before moving on to the next step.
Walk onto a patch of grass in the Route 207 area and open your PokeGear menu. Select the PokeRadar to activate the device.
Walk over to the rustling grass after activating the PokeRadar. This will cause a Wild Pokemon encounter. Even with the PokeRadar you have a 12 percent chance of encountering Larvitar, so you will likely encounter multiple Pokemon before reaching your intended target.
Weaken Larvitar with your strongest special moves. When Larvitar is weak, select a Pokeball from the menu to capture it.