Help on setting up mulitple (2-3) NetGear NightHawk - AX8 WIFI Range Extenders to a MOFI Router

Looking for help on how to set up mulitple NetGear - NightHawk AX8 WIFI Range extenders on my MOFI Router.   I have successfully set up 1 NightHawk AX8 on my MOFI Router, yet running into problems with adding a 2nd AX8 to my router.   I live in a rural area and have several buildings on my property (house, detached garage, workshop) that I want to extend my WIFI signal to so I can use the same network router. 

Looking for step by step set up instructions on how to have multiple range extenders using the same WIFI Router.  When I login to the NetGear Installation Assistant I am unable to find a menu on adding additional extenders to my network?  When I use the WPA set up instructions, not able to join the 2nd AX8 Extender to the MOFI Router.

Do I need to pair the extenders so they are seen as one?   Or do I add the MAC Addresses for the AX8 Extenders in the MOFI - ACL (Access Control list) ?   

Appreciate the help.

Camano-Belle