1. First of all you need to become member of http://sandbox.orkut.com/

2. For this you have to apply for developer from http://code.google.com/support/opensocialsignup/

3. It will take around 48 hours for confirmation.

4. After confirmation you can start making your Orkut Apps from http://sandbox.orkut.com/MyApps.aspx.

5. After reaching http://sandbox.orkut.com/MyApps.aspx you can see "add application" button. So enter your xml url here and you can see your Orkut Apps.

6. After creating your apps submit your apps in Orkut Directory.

For more information about Orkut Application you can refer Orkut Development guide.

http://www.windowsvistaplace.com/how-to-create-orkut-application/othersoftware
http://code.google.com/apis/orkut/docs/orkutdevguide/orkutdevguide-0.8.html
http://orkutapps.com/