Linkys to old Belkin router

I am very noob and do not understand majority of this. I got this all from Googling and watching videos but somehow I am not getting this to work even though I believed I have followed directions from what i found here on this reddit group too.

I am trying to link my Linksys WRT1200AC to an old Belkin wireless G plus mimo router to extend my wfii network.

The Linksys is connected to the modem and the Belkin is the access point.

However, when i set up Belkin as the access point via the site i type in for the ip address, it projects Belkin's wifi as a new SSID instead of the wifi I have set up on Linksys. It is unsecured and I do not want that. I tried to change the SSID on the belkin site to the same name as Linksys but it just creates a new unsecured wifi. I added a password but my linksys wifi says there is a privacy concern because it is blocking DNS now.

I really don't know what I am doing now as I thought changing the IP address on the belkin router as an access point to extend my wifi was all I needed to do based on the info I found. I don't want a new wifi network from the access point that my whole neighborhood can use but just an extended one using the router. What am I doing wrong and is it still possible to extend my wifi with the old belkin at this point?

Advice is greatly appreciated.