Answer:
It would go like this:
I love apples(A)
You can make them into jam(B)
or maybe not(C)
but even apple jam wouldn't be as good as ham.(B)
Ok, so that was a rubbish poem, but you can get the rhyme scheme from it. The last word on the first line represents A, and the last word on the third line represents C. A and C don't rhyme, because they are different letters. The last word on the second line represents B, and so does the last word on the fourth line, because they rhyme.
So, basically, In an ABCB rhyming poem The first and third lines won't rhyme, but the second and fourth will.
Hope that answers your question. :)