If you have experience programming in PHP and API's and you plan to only use the data from your own account the simplest method would be to use GAPI http://code.google.com/p/gapi-google-analytics-php-interface/
With this you hard code your Google email and password to gain access it does not use OAuth.
If you are building a 3rd party application that others will use to gather data. You should absolutely use OAuth so tokens are used and not passwords. For this read the OAuth guide https://developers.google.com/gdata/articles/oauth
Then use the Analytics data explorer to authenticate, and build a query URL. Take this URL and go to the OAuth Playground, go through the authentication process and post the URL. You will then see the XML response from Google Analytics with the data you wanted, now you can use the data however you want.
Google Analytics API v3
PHP Beta libraries from Goolge