How do you find all four hidden items in mike v skateboard party app in the first place?

Look! One is by the slides and another is by the Olympic pool/ secret area. The Olympic pool can be found easily. Skate board around the map until you see a reddish brown ramp. Down the ramp is the Olympic pool. The third item is up the stairs along the streets in a little shady area that looks like where you could walk in to a store. As for the fourth I cannot recall where it was but I think it could've been on the top of the bus.