Using Composer:
- Install using composer
composer require clivewalkden/magento2-checkoutsuccess
- Enable the module
php -f bin/magento module:enable --clear-static-content CliveWalkden_CheckoutSuccess
- Database updates
php -f bin/magento setup:upgrade
- Configure the module in the Magento 2 Admin. Go to Stores -> Configuration -> Advanced -> Developer -> Checkout Success Testing Module