Lumen utilizes Composer to manage its dependencies. So, before using Lumen, make sure you have Composer installed on your machine.
Create folder lumen in htdocs, then open terminal, change directory to lumen and in composer
composer create-project --prefer-dist laravel/lumen
The next thing you should do after installing Lumen is set your application key to a random string. Typically, this string should be 32 characters long. The key can be set in the .env environment file. If you have not renamed the .env.example file to .env, you should do that now. If the application key is not set, your user encrypted data will not be secure!