You need to get the Fanuc option for controlled axes expansion. In many cases this is just a configuration parameter edit. It may require a firmware upgrade.
The best method is to contact Fanuc and purchase it. Some searching may lead you to what configuration parameter needs to be edited. Be warned that if the firmware does not support the function or you make a mistake when editing the configuration parameters, the machine will go into a system alarm mode. The only recovery is to initialize the control and reload all the control data (CNC parameters, DGN parameters, pitch comp table, and any builder or user macro programs).