No need to rebuild your entire contact list, just import it from your current application and format it to your address book in OS.

In order to import your clients, you will first need to Export them from current application.

This tutorial covers how to Export your Contacts from Gmail.

1. Click the drop down arrow beside the red “Gmail” in the top left corner of your Gmail page.
2. Click “Contacts”.
3. Click on the drop down arrow beside “More”, near the top of the page.
4. Choose which contacts you want to export.
5. Choose “Outlook CSV format (for importing into Outlook or another application)”.
6. Click Export, then “Save file” and click OK.
7. Type a name for the file in the “File name” field and choose where to save it.
8. Click Save.

Once you have your export file, you can now Import your Contacts into MYcarnegieOS!

See this article on Importing you Contacts