Once you have updated your app and perform testing on it, you will need to have it resigned before you can redeploy it an App Store (e.g., Google Play, Amazon).
Click Build > Clean Project.
NOTE: This will clean the project and render a fresh copy.
Click Build > Generate Signed APK and this time select use existing keystore radio button.
NOTE: You must use the SAME KEYSTORE when updating an app on Google Play.
Type a password for keystore and then click the Next button.
NOTE: If you enter a wrong password, you will get a message the says, “Keystore was tampered with, or password was incorrect” and you will not see any Alias in the drop-down box
[ADD SCREEN SHOT]
In the Destination and key/certificate checks dialog box that appears, click the Browser button and navigate to the APK and then change its name (e.g., myAwesomeApp_v2).
Click the Finish button to create a new version of the app. Optionally, browser to it to see it in the folder you selected.
Go to the Google Developer Console and click the Add New APK to Production and navigate to the new APK file and then click the Open button.
CHECK POINT: In the dialog box that appears, you should see the new Version code (e.g., 2), the new Version name (e.g., 1.1) and the Size of the app. In the What’s new in this version? text field, add what changes you made (e.g., fix bugs, new or updated features, updated to newer version of Android)
Click the Publish now to Production option.
CHECK POINT: You should see that a message that says “Your application has been published. It can take several hours until it is available throughout Google Play.