Percona Audit plugin, which does not start the MySQL server

First I installed the Percona Audit plug-in on our MySQL server (my MySQL server version is 5.5.38), then I stopped the MySQL server and then in the my.cnf file the varialbes like Added audit_log_policy, audit_log_rotation_size, audit_log_file_location, and so on. When I try to start MySQL, I see the error as an "unknown variable" audit_log_policy = ALL "", which does not start the MySQL server, so can someone help me fix this problem.