Need help with citizenship, social security, and being allowed to work?

I am a legal immigrant to the United States, I've been here for 13 years and am now 17. My mother obtained full citizenship approximately 4 years ago. Im not sure if that means I have full citizenship or not because frankly I have no idea how any of this works. The problem is that I want to get a job and from what I was told im not elligable to work because i didnt file for employment authorization and something else with my social security yet. Im already 17 and have things i want to do as a teenager but these things of course require money, cante earn money if im not able to even get a job. What exactly do I need to do to approve my information so I can start working? Are there any websites that can give me more information on this subject, how much will it cost, and what information do i need to give? Please and thank you.:)