# Step 1: Embed Surface Tag
1. Navigate to the `pages/_document.tsx` file.
2. Add the following code in the *Start of `` tag* section.
Check out the [**How to Get Site ID**](https://www.withsurface.com/docs/platform/traffic/surface-tag#where-to-find-your-site-id) page to get your site ID.
```tsx
import Document, { Html, Head, Main, NextScript } from "next/document";
import Script from "next/script";
export default class MyDocument extends Document {
render() {
return (
);
}
}
```
Using a verified custom domain? Add `data-custom-domain="forms.example.com"` to the Surface Tag. Follow the [custom-domain setup guide](https://www.withsurface.com/docs/platform/traffic/custom-domains) before publishing the change.