To use CloudFlare R2 Storage , register to Aws S3 and follow this documentation to get api details
Go to admin panel > CloudStorage, select AWS S3 as your default storage driver, and add your API key details here. After saving the api key, click on sync local file to cloud to sync your existing local file to Cloud Storage
S3 configuration reference
Read details: https://laravel-news.com/using-aws-s3-for-laravel-storage