Hello @duc.quach, I believe that customizing your certification is better through django admin, because you can make diffrent certificate templates per course and it’s easier.
If you choose to edit your therme directly you should use comprehensive themig and ovveride your scsss. Read this https://dehamzah.com/comprehensive-theming-on-openedx
But it is much more easier to create a certificate template through admin and add your css.
Check the following instructions:
Open Edx certificate template SASS
Additionally here you can find a template that is tested and to edit as you want
custom_cert.txt (7.4 KB)
Then you should enable certificates for your course through studio
You can watch this video
Configuring Open edX Certificates in Studio | https://www.youtube.com/watch?v=IJvMjou8e64
To activate certificates
Studio: Settings -> Certificates -> fill in fields and upload signatures (Mode -> honor, “Active” should be ticked)
Studio: Settings -> Advanced Settings -> Certificates Display Behavior: early_with_info
Studio: Settings -> Advanced Settings -> Issue Open Badges: true
Admin panel: Organizations -> Add organization (fill in Name and Short Name, “Active” should be ticked)
Admin panel: Link course -> Add link course (fill in course ID, select Organization, “Active” should be ticked)
Admin panel: Certificate templates (fill in name, fill in template, select organization ID, fill in course key (ID), choose “honor” mode, tick "Active”, select “All languages”)
To automatically award certificate, in LMS: Instructor -> Certificates -> Student-generated certificate
Activating honor mode
Admin panel: Course modes -> Add course mode (fill in course ID, select “honor” mode, fill in display name, fill in “0” under Price, fill in “usd” under Currency, rest stays empty)
*** You can see the certificate for honor mode, not audit…but you can make a certificate template for audit too.