Consider signed the application by example of development environment Eclipse.
You need to right-click on the project and select Android Tools > Export Signed Application Package.
Opens export Android-applications. In the first step suggest to choose the project you want to sign. If you select desired project, click on «Next». Farther you must select «Create new keystore». Click on the button «Browse» and enter the name of our keystore and select the place where it should be saved. Enter the password and the confirmation password, click «Next».
Fill the suggested field. Alias name can be anything. In the Validity set 50 years. Click «Next».
The last step - choice of where you want saved the signed apk. Use the «Browse» select the folder and click «Finish». After a short wait you can use the signed file for publication in Google Play.
In order to sign the application in next time must select «Use existing keystore». Select the file and enter the password. In the next window, select the alias you created and enter a password for it.