resources/views/app.blade.php に記述します
<!DOCTYPE html>
<html lang="{{ str_replace('_', '-', app()->getLocale()) }}">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title inertia>{{ config('app.name', 'Laravel') }}</title>
<!-- ここに記述します -->
<link href="/assets/css/my.css" rel="stylesheet">
<!-- Fonts -->
<link rel="stylesheet" href="https://fonts.bunny.net/css2?family=Nunito:wght@400;600;700&display=swap">
<!-- Scripts -->
@routes
@vite(['resources/js/app.js', "resources/js/Pages/{$page['component']}.vue"])
@inertiaHead
</head>
<body class="font-sans antialiased">
@inertia
</body>
</html>