Can’t connect extender to internet

[Juliewolfkiel]

I haven’t used extender in several years and can’t remember how I connected to my home internet

[plemans]

Start with factory resetting it. 

Push and hold reset for 7-15 seconds while powered on. 

Then follow the install guide. 

There's a support site with access to manuals, firmware, install guides, etc.
Go to https://www.netgear.com/support/
Type in your model number and from there it'll take you to the above.
Its a great resource to start with.