SUPR is the NAISS database containing information about users and projects. SUPR is a self-service portal for users of most Swedish HPC Centres. It is used for registering and updating contact info, applying for new projects, requesting membership in projects, and viewing statistics for the projects you are a member of.
When you have a SUPR account, you can join existing projects or apply for a new project. When you are in a project, you can apply for an account at HPC2N.