One of these websites can be found at www.wilton.com/idea/Mickey-Mouse-Clubhouse-Cake This also gives a great step-by-step guide on how to make the cake, as well as stating all the ingredients you will need when making your Mickey Mouse Clubhouse cake.
If you find it hard to follow written instructions with only limited photos, then another alternative would be to watch some YouTube videos from users that have made their own Mickey Mouse birthday cakes. You will find some very useful guides at www.youtube.com/watch?v=PR8msvI_3d0 and www.youtube.com/watch?v=_vXHqkf_PG8 Also, when you are playing the video, if you look to the right hand side of the webpage you will see many more similar videos that also have advice on how to achieve a great Mickey Mouse Clubhouse birthday cake.
Remember it should be fun to make the cakes so don't worry if your first try doesn't quite cut it. You can still enjoy eating it when you carry on with your second attempt. You should feel great pride when you achieve the standard you want and will be rewarded when you see the person's face who receives your cake.