If you are 16-18 years old you are entitled to find a job. However as a young worker there are rules that apply to ensure that you are kept safe and work in age appropriate environments.
Please ensure that you talk to your parents/carer about your employment aspirations to ensure that they are aware of this and that they are okay with your choices.
For full information about the rules regarding employment of young workers, please see the Citizen's Advice website here.
There are many websites that offer employment for young people and those aged 18+. Below are two links which can provide you with more information: