You can download the update to your device by heading over to Help > About on your Firefox browser or by pointing your browser to Firefox.com. You can also download the latest version and install the update manually using the links which follow:
You can download Firefox for Android version 22 directly on your device through the Google Play Store or by using the link which follows:
Firefox version 22 is primarily aimed at developers by adding WebRTC and asm.js support. Google began integration WebRTC (Web Real-Time Communications) back in October last year and Mozilla started their own tests since Firefox 18 beta. Now it seems the feature is ready for use. According Mozilla WebRTC will “integrate seamlessly with a users’ mobile phone and make voice or video calls and share files,” and with Web chat services has popular as they've ever been, this is a milestone in the timeline of Firefox.
Meanwhile Firefox for Android should get most of the features offered in the desktop version, but the change-log notes that doesn’t include WebRTC or asm.js support just yet.