You can share the rights for both entire folders and single items as follows:

1. Select the folder or item you want to share
2. Click the sharing tab. You will see an overview of the roles currently assigned for the folder/item. You can edit these in the first form on the page
3. Search for the user(s) you want to share the item/folder with by inputting his/her user name or email address in the search field
4. Once found, select the role you want to assign to this user(s)
5. Click assign local role to selected user(s)

If you want to assign local roles to one or more groups, repeat steps 1-2.

3. Check the box next to the appropriate group(s)
4. Select the role you want to assign to this group(s)
5. Click assign local role to selected group(s)