Publishing application is a process that makes it available for users to download on their android device and use it. In the Android development life cycle, publishing is the last phase where you are done with all development and testing-related activities, and finally going to publish your app. 

To publish your app, you need to export it as an APK file. After that, you can publish your app in the google play store. 
There are a few steps to export the application as follows:

1. First, you need to open the project in Android Studio and then you need to select the Build option that will show you a list of options. 
2. After that, you need to choose Generate Signed APK option.
3. After clicking Generate Singed APK from the list, it will ask you for some details like Key store path, Key store password, Key alias, and Key password. It will also show you two options such that Creating a new one and choosing an existing apk file. 
4. There you need to choose to Create New which will ask you the location to save the APK file with Build type. After providing all these details, you can simply click on Finish Button and it will be exported to that location without any problem. 

Now you need to register on Google Play to publish your application. You can follow the link to Google Play Marketplace using the URL: https://play.google.com/apps/publish/ 

After visiting this URL, it will ask you for some information and at last, you need to make a payment of $25 for publishing your first app on Google Play. This way, you can simply upload your APK file on Google Play and publish it for users.