1. Head over to the Firebase Console and either start a new project or pick one you already have.
2. Click on "Add app" and choose the "Android" platform.
3. Register your app by entering the package name, then follow the steps to download the google-services.json file.
4. Drop that google-services.json file into the app directory of your Android project.

1. Open up the project-level build.gradle file and add this classpath in the dependencies section:
   ```gradle
   classpath 'com.google.gms:google-services:4.3.10'
   ```

2. Now, open the app-level build.gradle file and apply the Google Services plugin at the bottom:
   ```gradle
   apply plugin: 'com.google.gms.google-services'
   ```

3. Add the Crashlytics dependency:

\`\`\`gradle
dependencies {
    implementation 'com.google.firebase:firebase-crashlytics:18.2.10'
}
\`\`\`

1. Sync your project with the Gradle files.

1. Open your application class (or create one if it doesn't exist) and extend Application.

2. Initialize Firebase and Crashlytics:
   ```java
   import android.app.Application;
   import com.google.firebase.FirebaseApp;
   import com.google.firebase.crashlytics.FirebaseCrashlytics;

   public class MyApplication extends Application {
   @Override
   public void onCreate() {
   super.onCreate();
   // Initialize Firebase
   FirebaseApp.initializeApp(this);
   // Optionally enable Crashlytics debug mode
   FirebaseCrashlytics.getInstance().setCrashlyticsCollectionEnabled(true);
   }
   }
   ```

3. Register the application class in your AndroidManifest.xml file:
   ```xml
   <application
   android:name=".MyApplication"
   ... >
   ```

1. To log non-fatal errors or exceptions, use this code wherever an error needs to be logged:
   ```java
   try {
   // code that may throw an exception
   } catch (Exception e) {
   FirebaseCrashlytics.getInstance().recordException(e);
   }
   ```
   This will record caught exceptions as non-fatal errors in Crashlytics.

2. For custom logs, use:
   ```java
   try {
   // custom log message
   FirebaseCrashlytics.getInstance().log("Your custom log message");
   } catch (Exception e) {
   FirebaseCrashlytics.getInstance().recordException(e);
   }
   ```

1. Go to the Firebase Console, navigate to Crashlytics, and make sure the initial setup is complete.
2. Use the test method provided by Firebase to check if Crashlytics is working:
   ```java
   FirebaseCrashlytics.getInstance().setCrashlyticsCollectionEnabled(true);
   FirebaseCrashlytics.getInstance().log("Testing Crashlytics setup");
   FirebaseCrashlytics.getInstance().recordException(new Exception("Test non-fatal error"));
   ```

Add this code in an activity and launch the app. Check for the reported non-fatal error in the Firebase Console under Crashlytics.