How do you make up a song for the keyboard?

C, E, G, E, C, E, G, E, A, C, E, C, A, C, E, C, F, A, C, A, F, A, C, A, F, F, F, F, F, F, F, F, F, F.

C, E, G, E, C, E, G, E, A, C, E, C, A, C, E, C, F, A, C, A, F, A, C, A, F----, F.

Hope it helps :)