Prior to importing course content you need to have created an export package of the content from your old Bb course, and saved that ZIP file to your local computer. See this FAQ for details on that process.
Excerpt Go to the new course, where you want the content to appear. Navigate to the the three dots in the top right of your course. Click Import Content.
Click Import Course Content.
Browse your computer for the course export ZIP file. Click Submit. Note NOTE: This process can take a substantial amount of time, even AFTER you've received a confirmation email. Be patient. Re-submitting the file will not speed this up and will only result in multiple copies of your course files.
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Click Import Course Content.
When the import process is complete, you will receive a confirmation email.