Want to change Network Password on N750 and connect to my extender which is a N300 Model

I currently have a N750 Model WNDR4300V2 and a N300 Model EX2700 extender, and all works well.  Has worked well for years.  However, some people in the family wants me to change the password to make it something simpler. 

I tries that without much success today.  It is easy to change password on the N750 from PC.

I get on Android tablet and view settings on the N300 Model EX2700 and don't find a place to put in the new password I just put in the N750.  Under Wireless settings I see my SSID which is Jer_EXT, channel number, wifi speed, and a field that says WiFi Password set same as existing network password.   Under the that password selection, I can select Same as existing or Use a different or None.  I am assuming this setting is for devices that connect to the N300 extender like TV, cameras, phones etc?  So I have it set as Same as Existing network.  I want the password to be the same to connect to Jer or Jer_EXT

Another setting I can see 7 devices are connected. 

Under Password, is a setting just to change my logon to the extender and 2 security questions in case I forget extender password.

Problem is I don't find anyplace to tell the extender the new password  I modifies on main wireless router N750 Model WNDR4300V2 via PC.   I put everything back to normal for now, but seems this should change and I am missing something.   Think I put this in back in 2015 and had no problems, but may have lost a few brain cell since then? 

Sorry for long post, hope it makes sense and not too many miss spellings.