Single SKU bundle functionality is installed automatically when you add the app to your theme of choice. You can check the status of the installation by heading to Settings → Installation. Please ensure you select the correct theme (the Current theme will be selected by default).
The installation process will install a single template in your current theme. The file is called
product.bundlebuilder.liquid and it will be located in your 'Templates' folder. This file ensures that customers are redirected to your bundle page correctly.