docs: nuxt install

Author: posva

docs/nuxt/getting-started.md

@@ -4,13 +4,21 @@
 The Nuxt module and this docs are a WIP. Things might not work yet.
 :::
 
-Install
+## Installation
 
 ```bash
 npm install nuxt-vuefire
 ```
 
-Add it to your nuxt config:
+Additionally, if you are using [SSR](https://nuxt.com/docs/api/configuration/nuxt-config/#ssr), you need to install `firebase-admin` and some other peer dependencies:
+
+```bash
+npm install firebase-admin @firebase/@app-types
+```
+
+## Configuration
+
+Next, add `nuxt-vuefire` to the `modules` section of `nuxt.config.js` and configure it with the credentials created in your app settings in your project overview (`https://console.firebase.google.com/project/YOUR_PROJECT_NAME/overview)`. You can find more details [in Firebase Documentation](https://firebase.google.com/docs/web/setup#create-project). It should look something like this:
 
 ```ts
 export default defineNuxtConfig({
@@ -20,7 +28,30 @@ export default defineNuxtConfig({
   ],
 
   vuefire: {
-    /* options */
+    config: {
+      apiKey: '...',
+      authDomain: '...',
+      projectId: '...',
+      appId: '...',
+      // there could be other properties depending on the project
+    },
   },
 })
 ```
+
+If you are using SSR with any auth related feature, you will need to create a [service account](https://firebase.google.com/support/guides/service-accounts) and provide a path to the credentials file in the `serviceAccount` property:
+
+```ts
+export default defineNuxtConfig({
+  vuefire: {
+    // ...
+    admin: {
+      serviceAccount: 'path/to/credentials.json',
+    }
+  },
+})
+```
+
+:::tip
+This service account file contains sensitive information and should **not be committed to your repository**.
+:::