By conincidence I'm training a Canadian PPL at the moment for his NPPL.
The website given above outlines exactly what needs to be done - assuming your PPL is current. If it is current, then you have to do all the written exams, the radio training and the two flight tests.
In my student's case his PPL had lapsed, so I simply wrote to the NPPL administrators with a suggested plan (ie 2 hours stall, spin awareness; cross country qualifier, nav training as req. and GH training as req. then flight tests). They wrote back and said fine, crack on.