Once you have the .jar file, you can run it via the command line. A common use case for developers and modders is to sign a single APK or a whole folder of APKs at once:
If you don't provide a keystore, the tool will automatically use a debug keystore provided within the JAR to make the process easier. Key Features
java -jar uber-apk-signer.jar --apks /path/to/your/apks
Are you planning to use this for or for signing a modified APK ? apksigner | Android Studio