Using Autotune PID Library

I'm using an Arduino using PID to turn solid state relays on and off to heat a vacuum chamber in various zones an the input is a measurement from 14 MAX37855s. The loop works pretty well, but zones change somewhat often and it's really a pain to dial them in every time, so I was hoping to get the zones autotuned.

My question is using the autotune library (linked), the example is less than vauge about how to actually use autotuning or how it works.

From the supplied "how it works", it makes it sound like it's stepping above and bellow a setpoint and calculating the P I and D values, but how is this implemented? Is this something that should be done every 30 seconds or so, or is this a one time thing? The example just calls it in the Serial read as a 1 or 0.

Basically, if anyone has used this library and is able to expound upon it's usage in this situation, I would greatly appreciate it! :)