You should have the official eng.pdn.ac.lk email in your FEeLS profile email. You can update your email in the FEeLS profile now. (How to do it)
If you don't have an eng email Visit this page for the instructions to apply. If you can't access your eng email please send your problem to email@example.com with the registration number and name through HOD.
(Note: eng email is mandatory to sit for the online exams)