Tell him to Right Click in the shortcut he's using to start the game. Select properties and, where it says Target, add this line:
OverrideAddress="5.*.*.*"
The * should be replaced by the correct numbers, reflecting his Hamachi IP. It should look similar to this:
"C:\Program Files\Microsoft Games\Age of Empires III\age3x.exe" OverrideAddress="5.*.*.*"
Now it should display his Hamachi IP in game
ESO - Walker
>> Napoleonic Era --> Visit their Homepage!
"Holy *****" > Thunder (Ensemble Studios)
Retired from AoE3. But I do play AoK HD in Steam now and then.