Go to your Marker App which you should've gotten it way back in the game. now just move a couple of steps until you see a flashing black face, like a rabbit or mouse, that shows where Mespirit is. Bring a Pokemon that knows Mean Look or has the ability Arena Trap. If you don't which Pokemon there are, I suggest a Golbat/Crobat or a Diglett/Dugtrio or a Nosepass with Block. Meeting up in the same spot with Mespirit is tricky. There are a few places it will landed most often. Outside Hearthome City, outside Veilstone City, near Route 202 and between Pastoria City and Lake Verity. You're best bet is either Veilstone or Hearthome. Choose either one and fly there. Keep entering and exiting the city and constantly keep watch on the Map. I caught mine outside Jubilife City after a few times of chasing it. To ensure that you can catch it, try freezing it. Ultra Balls or Timer balls work well on it.
