This is the real easy bit, just add a text box then make it Dynamic (using text options) and set the variable to:
_root.c
Put this text box where you want the percentage to be shown!
If you really want to display how many KB has to be loaded and how much has been loaded you need to add the code:
d = Math.floor(a/1024)+"kb";
e = Math.floor(b/1024)+"kb";
to the actions in the first frame.
This sets a and b to display the kb loaded instead of the bytes loaded. You then need to make dynamic text boxs with the varible '_root.d' for kb loaded and '_root.e' for kb total to load.