Below is a link to information provided by Pearson-Edexcel regarding Private Exam Candidates exam entry. Do remember that when intending to take an exam that you speak to the relevant people and get the right information on where exam centres are, dates, fees, forms etc.
Plan ahead, speak to your tutors and/or centre do not leave it until it’s too late. Don’t forget that there are entry and payment deadlines. Private exam candidates, or external candidates, do not have the same luxury as internal exam candidates, already enrolled at a host-centre.