What do i put in certificate box while connecting to VPN remote host?

Hi @Navdeep_Jimmy,
Welcome to the NethServer community. I am glad you found your way to the forums. We are here to help whenever you have questions.
Did you also find your way to the NethServer documentation? http://docs.nethserver.org/en/latest/vpn.html
If the vpn documentation for NethServer is not clear enough, please don't hesitate to ask again.