WordPress.org

1. Download and extract the plugin
2. Upload the inline-google-docs folder into the /wp-content/plugins/ directory
3. Edit file permissions through your FTP client to make the inline-google-docs/cache/ and inline-google-docs/cache/error.log.php writable.
4. Activate the plugin through the Plugins menu in WordPress
5. Go to Settings, then navigate to Inline Google Docs
6. Provide the plugin with your Google account login credentials
7. Input proxy settings if you are behind a proxy, then click on Save Changes
8. The plugin will display the document/spreadsheet id's for your documents and spreadsheets

File Permissions

Unfortunately, you need to correct the file permissions on your own as SVN automatically resets all file permissions on uploaded files. I recommend the following settings (assuming FTP user as codex and Web user as www-data):

-rw-r----- codex www-data some-file.php
drwxr-x--- codex www-data some-directory

As for the cache and error log:

drwxrwx--- codex www-data cache
-rw-rw---- codex www-data error.log.php

The UNIX commands are provided below:

cd /path/to/Wordpress/wp-content/plugins/inline-google-docs;
find . -type d -exec chmod 750 {} \;
find . -type f -exec chmod 640 {} \;
chmod -R g+w ./cache;