Update introduction.mdx

sdks/client-side/introduction.mdx

@@ -33,7 +33,57 @@ You can pass the following props to the `@dub/analytics` script to customize its
 
 ## Examples
 
-Check out some examples of the script in action:
+Here are some code examples to learn how to use the script:
+
+### Cross-domain tracking
+
+By default, the script already sets the `dub_id` cookie on a cross-domain level. This means that if you have the script installed on your marketing site (e.g. **example.com**), the cookie will also be accessible when your user signs up for your app (e.g. **app.example.com**).
+
+However, if you are installing the script on a subdomain (e.g. **app.example.com**), you will need to set the following option to make sure the cookie is accessible on the apex domain as well (e.g. **example.com**):
+
+<CodeGroup>
+```typescript React
+<DubAnalytics
+  cookieOptions={{
+    domain: ".example.com",
+  }}
+/>
+```
+
+```html Other
+<script
+  src="https://cdn.dub.co/analytics.js"
+  data-cookie-options='{"domain": ".example.com"}'
+/>
+```
+
+</CodeGroup>
+
+### Custom cookie window
+
+By default, the script sets the `dub_id` cookie to expire in 90 days. You can customize this behavior by passing the `cookieOptions` prop to the script:
+
+<CodeGroup>
+```typescript React
+<DubAnalytics
+  cookieOptions={{
+    expiresInDays: 60, // setting the cookie to expire in 60 days
+  }}
+/>
+```
+
+```html Other
+<script
+  src="https://cdn.dub.co/analytics.js"
+  data-cookie-options='{"expiresInDays": 60}'
+/>
+```
+
+</CodeGroup>
+
+## Open-source examples
+
+Here are some open-source code examples that you can referece:
 
 <CardGroup cols={2}>
   <Card