Here are some key points:
* Early Writing: Frost started writing poetry as a teenager, publishing his first poem in 1894.
* First Collection: His first collection, "A Boy's Will," was published in 1913, but it didn't gain significant attention until he moved to England in 1912.
* Critical Success: His second collection, "North of Boston," published in 1914, was a critical success and brought him wider recognition.
* Established Poet: From the 1910s onwards, Frost's career as a poet was well-established. He published several more successful collections and won numerous awards, including four Pulitzer Prizes.
Therefore, while there isn't a single point in time when he became a poet, his literary career gained significant traction around 1912-1914, with the publication of his first two collections.