Well, it doesn't matter which admin template you get, you'll still implement it the same. If you're looking for a free one, I suggest AdminLTE.
You'll need to create a master 'admin' template just like you have a master template for your application.
Next, split the navbar, sidebar etc into partials and include them in the admin.
Now you can extend the master template for admin views.
Example master template in views/templates/admin.blade.php
<!DOCTYPE html>
<html>
<head>
<title> Administrator Title - @yield('title')</title>
// admin css
</head>
<body>
@include('templates.partials.admin.navbar')
// if the admin template has code that houses the content etc, put it here and then yield the content within it.
@yield('content')
// javascript
</body>
</html>
myNewForForAnAdminRoute.blade.php
@extends('templates.admin')
@section('title') Home @stop
@section('content')
// content goes here
@stop
AdminLTE has a tutorial of how to integrate it within Laravel here if you're still confused: https://almsaeedstudio.com/blog/integrate-adminlte-with-laravel