Answer by taking a quote from the following article:

Edward "Ned" Kelly (December 1854 - 11 November 1880) was an Australian bushranger, outlaw, gang leader and convicted police murderer. One of the last bushrangers, and by far the most famous, he is best known for wearing a suit of bulletproof armour during his final shootout with the police. Kelly was born in the British colony of Victoria as the third of eight children to Irish parents. His father, a transported convict, died shortly after serving a six-month prison sentence, leaving Kelly, then aged 12, as the eldest male of the household.

Kelly's first documented brush with the law was on 15 October 1869 at the age of 14 when he was charged with the assault and robbery of Ah Fook, a pig and fowl trader of Chinese descent from Bright. According to Fook, as he was passing Kelly's house, Kelly approached him with a long bamboo stick, announcing that he was a bushranger and would kill him if he did not hand over his money. Kelly then allegedly took him into the bush, beat him with the stick and stole 10 shillings. According to Kelly, his sister Annie and two witnesses, Bill Skilling and Bill Grey, Annie was sitting outside the house sewing when Fook walked up and asked for a drink of water. Given creek water, he abused Annie for not giving him rain water, and Kelly came outside and pushed him. Fook then hit Kelly three times with the bamboo stick, causing him to run away. The visitor then walked away, threatening to return and burn the house down, and Kelly did not return until sundown. Historians find neither account convincing and believe that Kelly's account is likely true up to being hit by Fook but then Kelly probably took the stick from him and beat him with it. Kelly was arrested the following day for highway robbery and locked up overnight in Benalla. He appeared in court the following morning, but Sergeant Whelan, despite using an interpreter to translate Fook's account, requested a remand to allow time to find another interpreter. Kelly was held for four days and appearing in court on 20 October, was again remanded after the police failed to produce an interpreter. The charge was dismissed on 26 October and he was released. Sergeant Whelan disliked Kelly. Three months earlier when he had prosecuted Yeaman Gunn for possession of stolen mutton, Kelly testified that he had sold several sheep to Gunn that same day. The magistrate found Gunn guilty and fined him PS10. Furious that Kelly was not convicted for the robbery, Whelan kept a careful watch on the Kelly family and, according to fellow officers, became "a perfect encyclopedia of knowledge about them" through his "diligence". Following his court appearance, the Benalla Ensign reported, "The cunning of himself [Kelly] and his mates got him off", the Beechworth Advertiser on the other hand reported that "the charge of robbery has been trumped up by the Chinaman to be revenged on Kelly, who had obviously assaulted him". Fook described 14-year-old Kelly as being aged around 20 years. The following year, a reporter wrote that Kelly "gives his age as 15 but is probably between 18 and 20". Kelly, 5 ft 8 in (1.73 m) in height, was still physically imposing. When arrested, a 224-pound (102 kg) trooper was purportedly unable to subdue the then-15-year-old until several labourers ran to assist him and even then Kelly had to be knocked unconscious. CANNOTANSWER

How did he gain his fame?

15 October 1869 at the age of 14 when he was charged with the assault and robbery of Ah Fook, a pig and fowl trader of Chinese descent from Bright.