1. You can add css code in customizer. Or you can add it in theme options panel. http://prntscr.com/qn30if

2. I did not understand your question. Please tell me more details about it.

Best Regards,

• Where we add this css code? guide step by step
• if we want to add content, from where we add up?

Please use following css code to hide it.

.about-author.block { display: none; }

Best Regards,

How can we edit the "About Author" section in the post? Can we remove this section?