netbackup upgrade from 7.1.0.4 to 7.6

Hello everyone,

  I have netbackup 7.1.0.4 running on windows 2008 r2 OS.We are having two media servers and a master server.Also we are taking NDMP backups.Now,We are planning to upgrade to netbackup 7.6.Please let us know the step by step process of upgrade.