How do I set up a tool change operation?

And further down the rabbit hole I go! Happily, of course. The next operation I need to master is setting up a tool change. Can someone shed light on this topic? Does the G-Code automatically set up a window of time for me to swap the bit, or do I set it? I have no idea on where to start - please use small words.

Thank you!

This is all done in the controller. SheetCam just requests a change to the new tool.
For example you can tell Mach3 to ignore the tool change or to wait for you to change the tool then press cycle start.