Netgear Wi-Fi extender EX6300v3

What trouble are you having?

Details are key? 

What firmware is on it?

What router is it connecting to?

What method of setup are you using? 

Where does it error out? 

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.