JMESPath is an expression language that allows you to manipulate JSON. From selecting specific keys from a hash or only selecting keys based on certain filter criteria, JMESPath gives you a lot of power when working with JSON.
In my experience, the quickest way to get up to speed with a language is to try the language out. The JMESPath tutorial gives you a brief introduction to the language, but to really solidify the concepts you really just need to spend some time experimenting with the language.
You could accomplish this by using one of the existing JMESPath libraries, but there's an easier to way to accomplish this. You can use the JMESPath terminal. Either specify what JSON file to use or pipe the JSON document into the jmespath-terminal command.
The JMESPath terminal README has instructions on getting setup and how to use the JMESPath terminal.
Check it out, and feel free to leave any feedback and suggestions on the issue tracker.