You will need to set up a customer portal account to access Private pilot theoretical knowledge e-exams.
If you successfully pass the theoretical exams for the issue of a private pilot's licence, they will be valid for 24 months for you to submit an application for the PPL issue.
This period is counted from the date you complete your last theoretical knowledge examination.
Within these 24 months you must complete the flight training and pass the skill test, otherwise these exams will expire, and you will have to retake them.
Please see FCL.025 for more information related to exam validity.