While within your android project, navigate to Unity -> Assets -> Import Package and import your package.

Note: You can also double click on the package to import it.

Next, ensure that the manifest, gradle, and gradleProperties files can be updated. To do this, go to Edit -> Project Settings -> Publishing Settings and make sure that the following options are checked:

  1. Custom Main Manifest - This exposes the manifest file, allowing additional configurations to be made.
  2. Custom Main Gradle Template - This exposes the Gradle template file, enabling the addition of custom properties.
  3. Custom Gradle Properties Template - This exposes the main build options in Gradle so you can manually add any additional dependencies.