In Bonus Level 2, Harry controls the platforms. Use the buttons from right to left. Ron just jumps on the moving platforms.

Once Ron joins you, send the rat around the tube and the gate opens.

Both of you have to jump on buttons to get to the top area.

This is a quick level. You get the brick and are done.

Also in same starting area is Become a Builder, part 1 of 4

Build mode teaches you how to build rooms - it's easy and fun! Just make 2000 coins and you are done.

Lego Harry Potter Walkthrough