first you have to hit the mechakoopas and press b to pick them up and throw them at him after that avoid the little fire balls coming down, Peach will come out with a mushroom in case you need it,then avoid giant canonballs, and then same thing except the balloon thing is bouncing so don't get killed.
THE END

once inside u must go through number 2 door. climb all the way acoss, depending on whether u have mario or luigi this is your easiest possible choice:
Mario: 5
Luigi: 8
once pass you will enter a dark room hit the light and presume. once u come to browsers door enter and there will be a short clip thing. he will appear and throw mechachupas at u. hit him and through them up. that is just the first part good luck with the rest.

once inside u must go through number 2 door. climb all the way acoss, depending on whether u have mario or luigi this is your easiest possible choice:
Mario: 5
Luigi: 8
once pass you will enter a dark room hit the light and presume. once u come to browsers door enter and there will be a short clip thing. he will appear and throw mechachupas at u. hit him and through them up. that is just the first part good luck with the rest.