bought the used RAX200 AX11000 from amazon and unable to connect my internet

[sainyi]

how can i connect my router?

[RajaDaja]

What is exactly happening. "Unable to connect to the internet" 

Did you do a factory reset if you haven't.  I would do that first. There is a pin hold on the back. Press in for 20 sec and release.

Use web browser to get into your router settings by typing in :    routerlogin.com or routerlogin.net.   Sometimes it's the browser fault so try a different browser if the router login page fails to load.

Make sure you got your cables connected correctly. Coax > Modem > WAN port of Router.           Don't use the Night Hawk APP.

This should bring you to the welcome screen and you set up your router

[michaelkenward]

In addition to the sound advice from @RajaDaja you could tell us what modem you have in front of this router.

If you visit the support pages:

Support | NETGEAR

you can feed in your model number and find the documentation for your hardware.