First: When he throws the rocks at you you get close to him so the rocks hit him.
Second: When you walk on the ground the patches go up....you go to the right and push the rock under him and when the grass goes up it hits him :)
In Poptropica, if you wanted super powers, you need to beat the first five villains (Sir Rebral, Copy Cat, Ratman, Crusher, Speedy Spike) and then go to the Telephone Booth, where you answer the phone by clicking it twice. You now have super powers. You use them to beat Betty Jetty, who is on top a building Downtown.
There are several on YouTube, but you can find the solution at the related question below.
Sir Rebral is one of the 6 super-villains on Super Power Island. He uses his mind power to control physical objects.
Sir Rebral in the City Park on top of the broken statue. He is tearing up the Park with his mind power.
You can beat the 5 non-flying villains in any order. If you are working left to right, the next is Ratman in the sewer under the restrooms.
The restrooms are at City Park. Use the rock to help you beat Sir Rebral, then go into the sewer through either of the restrooms, to battle Ratman.
Sir Rebral is one of the 6 super-powered villains on the loose on Super Power Island. A strange meteor hit the prison and freed them, giving them all different super abilities. Sir Rebral can focus his mind power to move objects around, and has begun destroying the statues in City Park. Stop him by causing his angry actions to backfire, and he hits himself with rocks and then with a chunk of the ground. (see related question)
When you have beaten all five of the super-villains (Copycat, Speeding Spike, Sir Rebral, Ratman, and Crusher), the phone will continue to ring until you pick it up.
Sir Rebral - Sir Rebral is using his new mind power to wreck the statues in City Park, and will hit you with rocks. If you jump near him, he will be hit himself, get mad, and attack you by pulling up chunks of the ground. There is a large, loose rock on the ground by the restrooms. Place it so that it hits Sir Rebral when the ground pops it up. (The best place is a little to the right of directly under him.) Cuff him. (You get your ID sticker at the Prison.)
After you jump near Sir Rebral and one of his rocks hits him, he begins pulling up chunks of the ground to hit you. Move the rock that is near the restrooms, bringing it left until it is a little right of directly under Sir Rebral. The ground will toss it up and slightly left, hitting him.
On Super Power Island, you have to defeat 5 super-villains with your wits. Sir Rebral throws rocks at you with his telekinetic power. Dodge some and he will eventually get mad. He will yanking up and hurling chunks of the ground. When he does, move the sliding rock over to the left until it is a little bit to the right of directly under Sir Rebral. When he yanks up the ground, he will clobber himself with the rock. (see related question)
Dr. Hare is using mind-control rabbot ears on 24 Carrot island, and Sir Rebral is using telekinesis on Super Power Island. (see the two related questions)