UPGMA is a distance method and therefore needs a distance matrix. UPGMA is “ultrametric”, meaning that all the terminal nodes (i.e. the sequences/taxa) are equally distance from the root. In molecular terms, this means that UPGMA assumes a molecular clock, i.e. all lineages are evolving at a constant rate. In practical terms, this means that you can construct a distance scale bar and all the terminal nodes will be level at position 0.0, representing the present.
An amazing step-by-step tutorial how to use UPGMA can be found HERE, so study it thoroughly because you may need to construct a tree during the IBO using this UPGMA method. Thanks to http://edwardslab.blogspot.com.au/
Then, a very handy tool to learn about evolution can be found HERE.