To view the Security Details page, in the Properties pane, select View Security Details. The Default Security drop-down menu lets you choose between Public, Private, and View. This setting applies to all users unless otherwise specified.
To search for users and grant them security access other than the specified default, select Add Users/Groups. To add new users/groups, search for them, select the name, and then select Confirm when prompted. The list of users added appears below this option. The drop-down menu next to each name lets you choose between Full Access, Read Only, Read/Write, No Access, and Remove.