This guide will show you how to manage permissions for a Site, list and item within SharePoint office 365.
Steps for Site Permissions:
2. You must break permissions inheritance from the parent, select Stop Inheriting Permissions.
Steps for List Permissions:
3. Select Grant Permissions on the Permissions tab.
Steps for Item Permissions:
3. You must break permissions inheritance.
4. Select Stop Inheriting Permissions.
3. Click on “Share” button then the specified group or user will be added to the list and your document will have the specified unique permission.