Settings -> Security -> Device administration -> Unknown sources
2.Disabling the app,
Settings -> Application manager -> AppName -> Disable/Uninstall
3. Checking to see if "Device Administrators" has it blocked from uninstalling, and then trying the uninstall again.
Settings -> Security -> Device administration - > Device administrators
4. Factory Reset
( before factory reset , backup your contact and keep your online password to safe place . )