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Create a sandbox by following the steps in this Create a Canvas Sandbox Site with Middleware article.
Once you have a sandbox, you’re able to copy content from the course you need to share by using this Canvas to Canvas Course Import (course copy) article.
Finally, add the instructor(s) you need to into the sandbox by clicking People in the left-hand navigation. These steps can also be found in the Add or Remove Users From your Canvas Courses article.
Click on +People, type in their email address, change the role to Teacher, and then click Next.
The newly added instructor(s) need to Accept Invitation to this new course before they can see it on their Dashboard.
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