You can create different groups as group1,group2,group3. then add all respective users in groups. On each individual folders set permission explicitly for respective group and remove inherited permissions.
To achieve above thing alfresco share side inside site's documentlibrary, default there is no action visible to manage repository permissions.
The action you will see is just to manage site level permission.
So to enable repository side manage permission action, you need to modify share-documentlibrary-config.xml file where already this action has been configured.