You’re five easy steps away from becoming an APK-signing master. The instructions we’ll be following here will mirror those from Android Developers site

1. Click on Build > Generate Signed APK in the menu

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2. Click Next to build an APK for the app module

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Creating a keystore
A keystore is a file that acts as your signature, hence why we need one to create a signed APK for your app. This will help us run your app in case of any issues when we build your app on our specialized “Android evaluation machines.” If you already have a keystore file, you may skip to Step 5 to finish building your signed APK.

3. Click on Create New to create a new keystore file

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4. Fill in the fields to create your keystore and key as appropriate.

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You should save your keystore in a safe place on your computer. You’ll use this keystore to sign your APK, which is one of the requirements of putting your app on the Play Store. You should not share this file with anyone who doesn’t own your app. Therefore, you should not send us your keystore.jks file.
Remember to also add a password for your keystore and your key. A keystore can have multiple keys, hence why there are two different password fields here.

5. Generate your signed APK

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In the Generate Signed APK Wizard (see Step 3 for a screenshot), you can choose the appropriate keystore value, such as the one you just created, as well as the password fields. Then click Next. On the following screen, click Finish. After a moment, your signed APK will be created.