Pinning lists allows Twitter users to more easily access lists that they've either subscribed to or created themselves.
Since you are making requests on behalf of a user with the these endpoints, you must authenticate them with either OAuth 1.0a User Context or OAuth 2.0 Authorization Code with PKCE, and use the user Access Tokens associated with a user that has authorized your App, which can be generated using the 3-legged OAuth flow (OAuth 1.0a) or the Authorization Code with PKCE grant flow (OAuth 2.0).
Pinned List lookup
Pinned List lookup has one available endpoint that allows you to retrieve an authenticated user's pinned Lists. There is a rate limit of 15 requests per 15 minutes for this endpoint.
Manage pinned Lists
The manage pinned List endpoints allow you to pin and unpin a List on behalf of an authenticated user. For these endpoints, there are two methods available: POST and DELETE. The POST method allows you to pin a List, and the DELETE method allows you to unpin a List. There is a user rate limit of 50 requests per 15 minutes for both endpoints.