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You will be offered 2 options:
Template option is advised for developers who developed a template file for the certificate appearance.
Template files should be placed by default in the templates folder in graphical theme, and named like this: opigno_certificate__id or opigno_certificate__id__full
Example of file names for id number 2: opigno-certificate--2.html.twig or opigno-certificate--2--full.html.twig
Most of the time you will select Wysiwyg, that allows to define a Label (the certificate name) and a Body (the content of the certificate).
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