The first magazine is on the right side of the island. It is white. The next one is on the back side of the island. It is also white. The last one is inside the Kame House. To get inside, you must go to the left side of the house and go up the stairs. Give the magazines to the Master Roshi and he will give you two Zenzu Beans, some Herbs and 350 experience points. Raditz will then appear, followed by Piccolo. You will be transported to the forest where Raditz took Gohan.