...i´m sorry that your g5/protoolz gear didn´t come with a driving instructor included.
please check and try to understand your hardware, how it works and its capabilities (you have at least a mbox).
read your manuals and about midi in general, especially about the fact that
midi is not audio. then check if you need cables.
then try it with some free softsynths from the net.
...
then come back and ask if you still need help in a specific area.
peace jo