p, downwards makes you crouch, and from side to side makes you move sideways. Using these controls you have to avoid all the obstacles and collect coins.
The only parts of the game that remind you that Messi is a soccer player are the soccer balls that occasionally appear scattered across the setting. If you hit them, Messi will kick them and break the nearest obstacle. Really it'd make sense if the Argentine got the ball, dribbled through the missiles, went to another planet, made a wall with the coins, dribbled back through the missiles, and scored a goal. But no.
Messi Space Scooter Game is a game whose approach is crazy and also very unique: no other game lets you travel the planets atop a scooter while playing Messi.