If the function is not disabled by your institution, instructors can follow the steps listed below to remove a member from a course.
STEP1: access course Roster/Members page. Click the "Roster" tab on the left course menu.
STEP2: once you are on the Roster/Members page, find the student you plan to drop from your course. Click the gear icon on his/her entry and click "Drop member from course".
STEP3: confirm drop this member.
The removed member will no longer be in your course. However, their posts and assignment submissions will remain in the course.