Running javascript e2e tests on a local appium server

I'm wanting to run e2e tests written in javascript with mocha on an Appium server instance running a local android emulator. The app on test is an apk originally written in react-native.

On Windows I have the server up and running with an Android Studio emulator through using the Appium desktop app. The server all looks good and has the apk of the native app I want to test working fine. I also have a basic describe/assert test written in mocha that I want to apply to the app.

My question is what do I need to include (presumably in the test file) to make the tests actually test the emulator application? I'm finding the documentation pretty confusing and the sample code seems pretty specific to a different use case.

Many thanks for your help!