Lord Ramacandra was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Siva, He married Sitadevi, daughter of Maharaja Janaka

Expressions researched:
"He was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Siva"

SB Canto 1

Lord Rāmacandra was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Śiva, He married Sītādevī, daughter of Mahārāja Janaka.

SB 1.12.19, Purport:

Lord Rāma: The Supreme Personality of Godhead incarnated Himself as Śrī Rāma, accepting the sonhood of His pure devotee Mahārāja Daśaratha, the King of Ayodhyā. Lord Rāma descended along with His plenary portions, and all of them appeared as His younger brothers. In the month of Caitra on the ninth day of the growing moon in the Tretā-yuga, the Lord appeared, as usual, to establish the principles of religion and to annihilate the disturbing elements. When He was just a young boy, He helped the great sage Viśvāmitra by killing Subahu and striking Mārīca, the she-demon, who was disturbing the sages in their daily discharge of duties. The brāhmaṇas and kṣatriyas are meant to cooperate for the welfare of the mass of people. The brāhmaṇa sages endeavor to enlighten the people by perfect knowledge, and the kṣatriyas are meant for their protection. Lord Rāmacandra is the ideal king for maintaining and protecting the highest culture of humanity, known as brahmaṇya-dharma. The Lord is specifically the protector of the cows and the brāhmaṇas, and hence He enhances the prosperity of the world. He rewarded the administrative demigods by effective weapons to conquer the demons through the agency of Viśvāmitra. He was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Śiva, He married Sītādevī, daughter of Mahārāja Janaka.

After His marriage He accepted exile in the forest for fourteen years by the order of His father, Mahārāja Daśaratha. To help the administration of the demigods, He killed fourteen thousand demons, and by the intrigues of the demons, His wife, Sītādevī, was kidnapped by Rāvaṇa. He made friendship with Sugrīva, who was helped by the Lord to kill Vali, brother of Sugrīva. By the help of Lord Rāma, Sugrīva became the king of the Vāṇaras (a race of gorillas). The Lord built a floating bridge of stones on the Indian Ocean and reached Laṅkā, the kingdom of Rāvaṇa, who had kidnapped Sītā. Later on Rāvaṇa was killed by Him, and Rāvaṇa's brother Vibhīṣaṇa was installed on the throne of Laṅkā. Vibhīṣaṇa was one of the brothers of Rāvaṇa, a demon, but Lord Rāma made him immortal by His blessings. On the expiry of fourteen years, after settling the affairs at Laṅkā, the Lord came back to His kingdom, Ayodhyā, by flower plane. He instructed His brother Śatrughna to attack Lavṇāsura, who reigned at Mathurā, and the demon was killed. He performed ten Aśvamedha sacrifices, and later on He disappeared while taking a bath in the Śarayu River. The great epic Rāmāyaṇa is the history of Lord Rāma's activities in the world, and the authoritative Rāmāyaṇa was written by the great poet Vālmīki.