Try the Getting Started guide (http://phonegap.com/getstarted/) on phonegap.com. It will show you how to setup the PhoneGap developer tools which you can use to run an app on a mobile device. I'd recommend getting through those first steps and then continuing on to authentication and syncing.
Several storage APIs are available for PhoneGap/Cordova applications. See html5rocks. for a more complete overview and examples.
Thanks so much, have started with it - seems to be pretty easy to use at the moment.
A bit daunting..