Begin by identifying the different user roles and what data each role needs access to. Use RLS to filter data at the query level based on user roles. Assign roles within Power BI by creating security groups in the Power BI consultant service. Use DAX expressions to define row filters that restrict data. Test RLS thoroughly using different user scenarios to ensure the right level of data access. Regularly audit and update the security settings as user roles or data requirements change. Document the security setup for future reference.