Step 1: From your activity tab, go to the Settings tab.
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Step 2: Scroll down the settings and go to the "Restrict Access" section. Click "Add restriction".
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Step 3: From the list of restriction options, select "Groups".
Step 4: From the list of groups, select the group you want to have exclusive access to and participation in the activity.
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Step 5: Click "Save and return to course".