The easiest way to get started is to use the starter spreadsheet template. This has all the right information already loaded and gives you a sense of where to start.
To upload, go to docs.google.com and enter in your Google Account login (same as your gmail). This puts you in the Google Docs main screen. On the top right of the screen, click the Upload button.

On the Upload Files screen, first click the "Select files to upload" link and find the starter spreadsheet included in the zip file. Click on the file in the Select File window and click the Open button. Now, back on the page, click Start Upload.

When the upload has completed and you see a checkmark next to the file, click the file name link to open the file. Before we start editing the pages and adding content, we're going to publish this spreadsheet in a format we can use and then add it to the PHP file. In the spreadsheet you created, click the Share button on the top right and select Publish as a Web Page.

Select "Sheet1" from the top drop-down, then click Start Publishing. Under "Get a link to the published data," select "RSS" from the frist drop down then click the Cells radio button. Your screen should look like this when you're finished:
