How do you set permission in UNIX system?

Each file, directory, and executable has permissions set for who can read, write, and/or execute it. To find the permissions assigned to a file, the ls command with the -l option should be used.
For ex:-
-rwxr-x--- allows the user (owner) of the file to read, write, and execute it;
those in the unixgroup of the file can read and execute it;
others cannot access it at all.