A simple, easy to use Google Checkout integration WordPress plugin.
If you do not have a Google Checkout account already then you need to sign up for one before you start with this plugin. Go to http://checkout.google.com and follow their steps for signing up.
Once you have your Google Checkout account, you want to install this plugin either using the WordPress installer or by downloading the .zip file and extracting it under wp-content/plugins/lbak-google-checkout then activate it in the plugins menu in your WordPress admin panel and find the Google Checkout link under the "Tools" menu, click on it and enter the following details:
Your Merchant ID. This has to be set for the plugin to function. To find it, go to your Google Checkout account and look in the top right hand corner of the page, it should be there. Alternately you will find it in Settings > Profile.
The currency you are using. It's essential that you get this right as the plugin will not work if you specify an incorrect currency. If you are in the UK, enter "GBP" (no quotes) into the box and if you are in the US enter "USD" (no quotes) into the box. If you want to use any other currencies you will need to look up how to do that in Google's documentation (I'm not sure if they have support for any other currencies yet).
The rest of the settings on the Settings page can be left default if you want but I recommend having a play around with them to get a real feel for what they do and how they work. This will make it easier for you to customise how you want the plugin to look and feel.
That should be it! You're now ready to start adding products to your database and selling things. If you have any further queries please consult the Help/FAQ page in the plugin's menu.