We do generally suggest waiting to make that kind of change until after you've tried it and determined whether it is working for you or not. That way it is a little more obvious when you break it yourself
I would really suggest following this guide, top to bottom.
http://isboxer.com/wiki/WoW:Quicker_Start_Guide#Part_2:_Log_inThe guide is written such that ... if you follow it top to bottom, you can tell us the very first thing that doesn't work, and what that first thing is tells us what to tell you to look at.
For example... Step 4 tells you to turn on Key Maps and make sure Broadcasting Mode is turned off. We don't know if you did that, but if you have Key Maps off from logging in then it's not going to do much when you press your ISBoxer follow hotkey.
Step 5 says to invite your characters via Shift+Alt+I. You probably did it another way, and that is fine, but the instructions specifically use this method so we can determine that you have a) Key Maps turned on, and b) the ISBoxer Addon loaded. If either of those are false, Shift+Alt+I does nothing. This is information that is helpful to have BEFORE testing follow, so test it first.
Step 6, then is the Follow step. By this point you should have already checked that Key Maps are enabled, the ISBoxer Addon is enabled, and both are operating because pressing Shift+Alt+I invites your toons. If Shift+Alt+I does not invite your toons, don't bother with Steps 6 and beyond.
So... does Shift+Alt+I invite your team?