Follow these steps to create and attach a rubric to an assignment on Microsoft Classroom:

1. Open the assignment in Microsoft Classroom and click the Rubric tab.
2. Choose a Rubric type from the dropdown list.
3. Edit the rubric to your specifications by clicking the pencil icon beside each criterion.
4. Assign the rubric to the assignment by clicking Save Rubric at the top right corner of the page.
5. View the assignment to ensure the rubric has been attached.