Calendar blocking help for newbie

I’m new to editing plugins within WP and I want to add the calendar marking/blocking capability to my scheduler. http://docs.dhtmlx.com/scheduler/limits.html#howtoblockcertaindates

In which file do I add the include for the limit.js? I’ve looked in every logical place, but haven’t found the right spot.

In which file should I add my custom calendar block code?

Thanks in advance for helping out a newbie.