Yes, it's possible, but you'll need to lift the vehicle and have some special service tools to do it with. This is best left to professionals for many reasons. The question is: why do you think you need fluid? What is going on with your CVT?
RepairPal Certified shops can diagnose and repair your 2014 Nissan Sentra. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.