You apply to the programme through the university where you plan to do your masters project.
See links to the participating universities under ”About NABiS”.
Inform yourself about the application dates pertaining to the university you plan to join. Note that Sweden and Norway have different application systems and different rules regarding application fees. Note also that international students from outside EU/EES have to pay tuition fees when studying in Sweden. This is unfortunately also the case when Master’s students admitted to the Norwegian universities take courses within the programme given by any of the Swedish universities.