How do you setup WI-FI EXTENDERS

In addition to what is listed in the support article that led you here, I suggest that you contact the "wifi extender" manufacturer's support team and ask them.

Regards

Giulio

By reading the information that comes with the devices in question. We can't see your computer much less read your mind. These are third party devices and they have their own instructions.

That is outside the remit of this site but, depending on the manufacturer, read the installation instruction manual.

You can then connect iphone to the SSID of the extender.