Smeargle is a special Pokémon, where his only attack is Sketch.
Sketch copies an attack from a Pokémon with the same force and position (If using a Skecth m1, will copie m1 attack of the desired Pokémon). To copy any attack using the Sketch follow this:
1st Step: Take out the Smeargle of the Poké Ball and keep in mind which attack and what Pokémon you want to copy.
2nd Step: Use the Sketch according to the number of attack you want to copy, if you want to copy the 'm1' use sketch 'm1'.
3rd Step: Click in Order button and then use in the Pokémon you want to copy the attack.
After copying an attack, this attack will be permanently on your Smeargle, so think well before you use it.
The number of Sketch is according to the rarity of Smeargle, you can find Smeargle with 2-8 Sketch.