By Sri Swami Sivananda

While Narada was touring the three worlds, he met the Sapta Rishis: Atri, Bhrigu, Kutsa, Vasishtha, Gautama, Kasyapa and Angirasa. Envious of their exalted state, Narada wished to become the most famous of the Rishis. He went to Sri Ganesha and asked him how he could become greater than the Seven Rishis. Sri Ganesha instructed Narada how to observe the Karthikai Vrata and initiated him into the worship of Lord Skanda. Having performed this Vrata for twelve years, Narada achieved his aim by the grace of Lord Subrahmanya.

References:

 Sivananda, Swami. Lord Shanmukha and His Worship. World Wide Web edition. India: Divine Life Society, 2000.