You should cite a post on X (formerly Twitter), Instagram, or other social media using the same format of core elements that you use for other sources. In this case, the “author” is the author of the post, with their handle (if it is different from their name) in parentheses. The title is the first part of the post (if text) or a description of the image (if the post is an image). The container is the platform (X, Instagram, or another social media platform). The location is the URL, and the date is the date posted rather than the date accessed.
Example
Kayyem, Juliette. “A school district police department that did not need to exist should never exist again.” Twitter, 7 Oct. 2022, https://twitter.com/juliettekayyem/status/1578447720720699392.