Key points from this section:

• Establishment of the First Presidency: This revelation, given on March 8, 1833, was a significant step in establishing the First Presidency of the Church, with Sidney Rigdon and Frederick G. Williams called to serve as counselors to Joseph Smith.
• Keys of the Kingdom: The section emphasizes that the keys of the kingdom are committed to Joseph Smith and through him to the Church, ensuring the continuity of divine authority.
• Preaching the Gospel: It instructs that the gospel is to be preached to all nations, with a promise that everyone will hear the fullness of the gospel in their own language."

Read this chapter for free at https://byustudies.byu.edu/online-book/doctrine-and-covenants-contexts/section-90.