How do I allow a device in IPv6 Firewall?

Installing and Using OpenWrt Network and Wireless Configuration
10

So what file do I need to edit? I mean where do I copy and paste the code above.

uci add firewall forwarding
uci set firewall.@forwarding[-1].src="wan"
uci set firewall.@forwarding[-1].dest="lan"
uci set firewall.@forwarding[-1].family="ipv6"
uci commit firewall
service firewall restart