There are 3 ways get this done ..
HTML5 Webstorage, IndexedDB and good old Files . More importantly, the Tizen wearable sdk comes with sample code
HTML5 WebStorage Example.
Since your apps are written in HTLM5 and compiles using a webbrowser-like runtime engine, you can use the HTML5 Web storage paradigm for data storage and retrieval.
localStorage.setItem("lastname", "Smith");
// Retrieve
document.getElementById("result").innerHTML = localStorage.getItem("lastname");
You can read more about it here ..
http://denvycom.com/blog/how-to-store-data-in-your-gear-2-apps/