Robots.txt file plays vital role allowing your website to be displayed in search results pages. If you want to prevent search engines from indexing parts of your storefront, you can update your search engine robots files.
In bigcommerce there editing robots file is quite easy task.
Follow these simple step:
1. Login to your storefront of bigcommerce https://login.bigcommerce.com/login
2. Go to Settings › Store Setup › Store Settings › In Website tab > scroll down to Search Engine Robots section.
3. Now here you can add your code to http or https version as your website present.