You don't need to change anything in the main configuration (_config.yml), just you need to change the baseURL when you host this template.
You will find every parameter in `_data/parameters.yml`` this file.
You can set the main menu and footer menu also from _data/parameters.yml, just follow the existing loop for creating a new menu item. This theme also supports the dropdown menu.
For creating a new blog post, you need to go to the _posts folder and create a new file. Make sure you are creating this file name with the existing post name structure which is year-month-date-post-name.md. (i.e 2020-02-06-my-awesome-blog.md). Then follow the existing post front-matter to configure it. Or you can simply copy an existing post and replace its content.
This is the same process for the blog post. Copy an existing author file, and replace your content and file name.
Another page customization (like about, contact) is very easy. You can see the other page in the _pages/ folder. Find the page that you want to customize, and change the content from it. If this page has any loop item, then follow the existing loop to create a new one.