The easiest way would be to put all the libraries on to an external hard drive
then you would want to open the library with the most music then click and drag the other libraries into itunes ...
this will then bring all the music and pictures together
if you don't have an external hard drive the next best thing would be to turn home sharing on, on each library and then copy them to one master computer
You can then just move songs by clicking and dragging in itunes.
Brilliant....so easy, Thanks