You have no Run configuration for your project. You can see it in the top of the screen - Add configuration. Click on it and create new Configuration.
then click on the build:
then click on the Generate Signed Bundle/APK:
After that this window will be shown, select apk and click to next:
Below keystore path click on create new:
After clicking on create new, this window will be shown. Now fill the details and select the path of keystore and keystore file name, Don't forget to add Validity for up to 1000 years:
After it has been successfully created, please replace app.jks in the android/app folder with the jks you created earlier, then open the key.properties file and input the data you have storePassword=remember
keyPassword=remember
keyAlias=key
storeFile=app.jks
