1. Head over to the Firebase Console: https://console.firebase.google.com/.
2. Click on "Add project" or pick one you already have.
3. Fill in the details, agree to the terms, and hit "Create Project."
4. Once your project is ready, click "Continue."

1. In the Firebase Console, go to the Project Overview.
2. Click the gear icon (⚙) and select "Project Settings."
3. Under the "General" tab, scroll down to the "Your apps" section.
4. Choose your platform (iOS/Android/web) and follow the setup instructions to add Firebase SDK to your app.

1. In the Firebase Console, navigate to the "Authentication" section.
2. Click on the "Sign-in method" tab.
3. Pick the OAuth provider you want to set up (Google, Facebook, Twitter, GitHub, etc.).
4. Enable the provider and fill in any required fields, like Client ID and Client Secret.
5. Click "Save."

1. For web applications:

   • Add Firebase SDK to your index.html or use npm.
     ```html ```
   • If using npm:
     ```bash
     npm install --save firebase
     ```

2. For Android:

   • Add the Firebase SDK to your build.gradle (project-level) file.
     ```gradle
     classpath 'com.google.gms:google-services:4.3.10'
     ```
   • Add the dependency in build.gradle (app-level).
     ```gradle
     implementation 'com.google.firebase:firebase-auth:21.0.1'
     ```

3. For iOS:

- Add Firebase CocoaPods to your `Podfile`.
\`\`\`ruby
pod 'Firebase/Auth'
\`\`\`

1. For web applications:
   ```javascript
   import { initializeApp } from "firebase/app";
   import { getAuth } from "firebase/auth";

   const firebaseConfig = {
   apiKey: "YOUR_API_KEY",
   authDomain: "YOUR_PROJECT_ID.firebaseapp.com",
   projectId: "YOUR_PROJECT_ID",
   storageBucket: "YOUR_PROJECT_ID.appspot.com",
   messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
   appId: "YOUR_APP_ID",
   };

   const app = initializeApp(firebaseConfig);
   const auth = getAuth(app);
   ```

2. For Android:
   ```java
   import com.google.firebase.auth.FirebaseAuth;
   import com.google.firebase.auth.FirebaseUser;

   FirebaseAuth auth = FirebaseAuth.getInstance();
   ```

3. For iOS:
   ```swift
   import Firebase

   FirebaseApp.configure()
   let auth = Auth.auth()
   ```

1. Google Sign-In for Web:
   ```javascript
   import { GoogleAuthProvider, signInWithPopup } from "firebase/auth";

   const provider = new GoogleAuthProvider();
   signInWithPopup(auth, provider)
   .then((result) => {
   const user = result.user;
   // Use user information or token here
   })
   .catch((error) => {
   // Handle Errors here.
   console.error(error);
   });
   ```

2. Facebook Sign-In for Web:
   ```javascript
   import { FacebookAuthProvider, signInWithPopup } from "firebase/auth";

   const provider = new FacebookAuthProvider();
   signInWithPopup(auth, provider)
   .then((result) => {
   const user = result.user;
   // Use user information or token here
   })
   .catch((error) => {
   // Handle Errors here.
   console.error(error);
   });
   ```

3. Sign-In for Android:
   ```java
   import com.google.firebase.auth.AuthCredential;
   import com.google.firebase.auth.GoogleAuthProvider;

   GoogleSignInAccount account = completedTask.getResult(ApiException.class);
   AuthCredential credential = GoogleAuthProvider.getCredential(account.getIdToken(), null);

   auth.signInWithCredential(credential)
   .addOnCompleteListener(this, task -> {
   if (task.isSuccessful()) {
   FirebaseUser user = auth.getCurrentUser();
   // Use user information or token here
   } else {
   // Handle Errors here
   }
   });
   ```

4. Sign-In for iOS:
   ```swift
   import FirebaseAuth

   let credential = OAuthProvider.credential(withProviderID: "google.com", idToken: idToken, rawNonce: nonce)
   Auth.auth().signIn(with: credential) { authResult, error in
   if let error = error {
   // Handle Errors here
   } else {
   let user = authResult?.user
   // Use user information or token here
   }
   }
   ```