First off, you need Tracker 3 from SymbianWare.
|Once you've installed them, drag and drop the .ZTR file to DOCUMENTS on your P900. Open FILEMAN. The file you just uploaded should be in your DOCUMENTS/MEDIA FILES. Hightlight .ZTR then click FILE then select MOVE. A window will pop up asking where you want to move it. Scroll through to C/SYSTEM/APPS/TRACKER/SKINS and then submit it. Open TRACKER then click START then select SELECT SKIN then select .ZTR|