Today I'm trying to make my new theme. In this part, I can't customize this part. How can I do this.
I am not sure exactly what you want to change. But to the right, you can "add an activity or resource" or "edit" the topic.
"Edit" shows up in many places. This is one way to customize your course (and Moodle).
"Edit" shows up in many places. This is one way to customize your course (and Moodle).
What version of Moodle are you running please?