You need to forward the port that the interface uses to the IP of your device (192.168.0.2) (80 if you’re using lighthttpd or 8080 if you’re using the built in web interface).
Then when you’re out of the house you need to use your internet connection IP address.
You can find that by going to www.whatismyip.com when you’re inside the house. This may be dynamic and change every so often. A dynamic DNS service like no-ip.com is useful.