Please go learn about the command shell. Whether or not you realized it when you purchased the box, you're running a Unix server, and sooner or later you'll need to know how to use the command shell. This whether to make a configuration change that the GUI doesn't allow for, or to debug something. The effort and the investment here spent learning about bash (and tcsh) and the shell (and a text editor such as nano, and shell commands including cd, ditto and chown shown in that script) will pay you back dividends.
As for using nano, here is a "hello world" example:
Launch Terminal.app.
The $ is the command prompt. You're not entering that in what I've shown here.
$ nano example.sh
Then enter the following text exactly as shown into the nano editor window:
#!/bin/bash
echo 'hello world'
Then press ^X to exit nano, answer Y (yes) to write the file, and accept the filename offered.
Then the following shows the file contents, makes the file executable, and executes it:
$ cat example.sh
#!/bin/bash
echo 'hello world'
$ chmod u+x example.sh
$ ./example.sh
hello world
$
To close the shell session, you can enter
$ exit
Yes. The shell is cryptic. It's also very powerful. There's a command line administration manual in the [Mac OS X Server documentation set|http://www.apple.com/server/macosx/resources/documentation.html], and there are various introductions to bash and tcsh around the network.
FWIW, bash is the default shell for new installations and newly-created users, but tcsh is around and works nicely, too.