for unsigned i used command
$ cordova build --re
For you to be able to install the unsigned package in your device, you need to allow installation from unknown sources. It can be done in Settings -> General (tab) -> Security where you need to check the Unknown sources check box. After that the install should work.
If you want to sign your application to be deployable to for example Play store, you need to refer to Android tutorial on that subject. you can also find steps for this from Stack Overflow. Once you have signed your .apk, you don't need to allow the unknown sources anymore.