Rule 10, Section 2 of the NFL Rulebook on free kicks after a fair catch
According to Rule 10, Section 2, Article 4, "After a fair catch is made, or is awarded as the result of fair catch interference, the receiving team has the option of putting the ball in play by either: (a) a fair-catch kick (drop kick or placekick without a tee) from the spot of the catch ... or (b) a snap from the spot of the catch."
And, according to Rule 10, Section 5, Article 3: "On a free kick following a fair catch all general rules apply as for a field goal attempt from scrimmage."