All Administrators and Super Administrators have full access to the code. For more information about user roles please check this article.
Your themes are located in Customize > Themes. There are 12 options availabe and all of them are fully customizable!
At https://helpjuice.com/knowledge-base-examples you will find some of the best knowledge base examples!
Don't worry, you don't even have to touch the code! You can always request help from our team and we will customize the code for you. For more information on how to submit a customization request check this article.