Go to the tab "My Applications" and find the application you want to publish. Next, click on "Publish" button in the application dashboard.
In the pop-up window select Google Play.
After that, you will be redirected to the publication page. Click on the "Submit myself" button.
You will be redirected to the page where you may build and download your application. Since we need to download a build, go to the tab "Download Android Build". After that, the building of your app will start.
If you publish your app for the first time, it will be better to change the version of the build to 1 or 1.0. It is not recommended to publish your app for the first time with a version that differs from 1 or 1.0.
After completing the build of your application, you can download it by clicking on "Download" link. The resulting apk-file is needed to download the application on Google Play. Also, the file can be directly installed on the device.