Hi @czhong ...
I am not sure that Canvas Community folks will be able to answer this question for you. Are you asking about something within the Canvas LMS (Learning Management System)? I am not really aware of any ways to do drawings in Canvas like you describe, so I wonder if you might be using something else called "Canvas" or maybe are you using "Canva" (which is a completely separate website not related to Canvas)? If you are taking a course at your school that uses Canvas as their LMS, you may need to reach out to your instructor directly to ask specifics about your drawing. You can contact your instructor by following the steps in this Guide:
How do I get help with Canvas as a student?
Hopefully this will help you. Good luck!