Network settings can also be configure manually.
To do so open the Settings Application and locate the Ambify entry.
Enter the IP address of your Hue bridge and switch "Use Manual Settings" to ON.
If you don't know the address of your bridge please have a look at the following article.
Once completed, head back to the actual Ambify app and go through the setup again, this time Ambify will not attempt to discover your bridge but use the address supplied in the settings instead.