A utility called CACLS.EXE comes as standard with Windows, and can be used from the command prompt. Read the help with the CACLS.EXE program (cacls /?).
To give user “john” Read access to a directory called “files” enter:
CACLS files /e /p john:r
/e is used to edit the ACL instead of replacing it, therefore other permissions on the directory will be kept.
/p sets permission for user:<permission>