Huffman Tree

I have to create a Huffman Tree. I have prepared the Priority Queue. the problem is arising while creating the tree as it is generated bottom-up. Can you please give any idea about how to do that?

There are a variety of tutorials online about how to do this (see Huffman Tree Tutorial - google and A quick tutorial on generating a huffman tree). Where exactly does the problem lie? What have you done so far?

Thanks...a lot....it's done.....