How does JIRA authorization work?

Question

JIRA

Guys who understand Jira. I want to create an addon in the marketplace, but I have problems with authorization. I can not get data about projects, cards in any way. I read the documentation many times about generating a jwt token in order to access data, but nothing comes out, it gives 401 Unauthorized. How authorization works, how to get an Access Token that could read the necessary data? I need to link a user from my database to a Jira user and count their projects, cards, attach webhooks, etc.
I created atlassian-connect.json, added lifecycle. Used clientKey and sharedSecret to create a queryHashString to run queries, still fails