There are three ways using which you can your product listing to Google Base. They are :

1) One at a time

You can use web based listing adding tool provided at the Google Base itself to add one listing at a time. This way works best if you have only few product listings to add.

2) Data feed

Useful for adding a large number of products at once. You upload data feed file by using the browser itself or by connecting through ftp.

3) API

Most flexible way to add product listings. Yiou can code your current ecommerce platform to add product listing automatically to Google Base and to keep it synchonised.

I'll be concentrating on third way to add product listings. In my next post i'll show you how to do it.