On the launcher, press the Menu button. Chose "Manage Applications". Wait a while (OK, more like half an eternity) and look for the application in the "Downloaded" or "All" tabs. Tap it. A dialog comes up asking you if you want to "Force Stop", "Uninstall", "Clear Data" and "Move to Phone" (if it's on SD and you want to move it back) / "Move to SD Card". You can move it/uninstall it by pressing the appropriate button.