aviation is full of different carriers and activities. you will need to give more information as to what you would like to do in aviation.
Answers can be from start flying to get a pilots license, or an apprenticeship at a avionics manufacturer, or get a job waiting tables to gain service industry experience or about 1000 other things.
"career in aviation" includes jobs in almost every field of economic activity from researching alternative fuels to building runways, to designing navigation devices, to economic modeling, to driving aircraft, to driving the blue water wagon.