Before using a file as a shell script you must change its access permissions so that you have execute permission on the file, otherwise the error message Permission denied is displayed.
To run the shell script, simply type its name at the prompt. The commands in the script will then execute one at a time as though you were typing them in at the terminal.
To give yourself execute permission for the file containing the script use the command:
$chmod u+rwx filename
The +rwx after the u allows you to read, write to and execute the script: no one else has permission to read, write or execute.
To give other users permission to read and execute but not alter the shell script use:
$ chmod go+rx filename