Confused about how to to set up things between this plugin and tracking service

Hello, sorry I’m newbie and don’t understand about how the plugin works. I’ve just bought the plugin and not sure if it suites my need.

I’ve added a tracking number into an order. But when I search this tracking number in the search bar, no tracking template shows up. A staff told me to use tracking service but I don’t know to do that. I’ve tried with Aftership but it says I have to pay to get the API. Is there any free API?

I couldn’t find any clear and specific tutorial video about how to set things up between this plugin and tracking service. This is very confused.