Hi!

I assume you installed the app in the Firefox OS Simulator, right? If that's the case, you can click and hold on the app you want to uninstall. The app will icon will start pulsing and an "X" button will appear to its upper left. Click the "X" to uninstall the app.

I hope that helps you! Please feel free to post back if you need more help.

No I installed it directly using firefox marketplace

Oh, I see; you installed it to Firefox for desktop. My apologies for any confusion; please disregard my previous post.

I'm not sure if the process is the same in Xbuntu, but at least for Ubuntu, you can uninstall the app by right-clicking its icon on the Launcher and clicking the Uninstall button.

I hope that helps!