API Access Token

[dkim0109]

https://pastebin.com/zx9FwZEs

This is what my code looks like so far. I followed the Spotify Web Api Documentation, and it says:

Response On success, the response will have a 200 OK status and the following JSON data in the response body.

How do I access the response body to get the access token? First time working with APIs and a bit confused.