http://isboxer.com/wiki/WoW:Quick_Start_Guide

Section 7 of that guide shows you how to add additional keymaps but read the entire thing anyway. This guide
can be found in the ISBoxer Wiki which is directly implemented into ISBoxer (it's all of that jumble of text
located in the upper right pane) and also accessible through the Help menu located in ISBoxer.

Also, this: http://isboxer.com/wiki/FAQ