Where do you find the egg containing the Pokemon Manaphy in Pokemon Ranger?

First you have to beat the Game and get the Ranger Net.

In Ranger Net Hold X and R & Press Left To Unlock Password Option Then Input The Following Codes For Your Language of Game.

American Version- P8M2-9D6F-43H7

European Version- Mg35-Cpb8-4FW8

Spanish Version- C58f-t3WT-Vn79

Some Portugese Versions- C58f-t3WT-Vn79