* Through your school or college: Most schools and colleges will provide instructions on how to access your results online via their own portal or website. They'll usually email or post this information to you before results day. This is often the primary method. Check your school/college's website or any emails they've sent.
* Through the exam board (less common): Some exam boards *might* offer online access, but this is less frequent. You'd need to check with your specific exam board (e.g., AQA, Edexcel, OCR, CCEA, WJEC/Eduqas) for their specific instructions – it's unlikely they will have a universal system for all students. Schools usually act as the intermediary.
In short, your school or college is the best and usually only place to find out how to access your results online. Contact them if you haven't received any information before results day.