Registering Plant Tycoon is easy and here are the steps:
1)Start the game (make sure you are in the main screen where you see all the pots)
2)Click on the drop down menus(this varies from device to device but there is always a button to activate the drop-down menus)

On most of the devices: click on the second button on the left side of the graffiti area
On the Tungsten C: click on the BLUE BUTTON +

(don't have to hold them down simultaneously--but first click the blue button and then the other one)
On the Treo 600: click on the MENU button on the keyboard
3) Select help --->register and you will find in bold your "Hotsync ID" and a place to enter your code
4)Voila