I installed the master and installed three extensions: JCE, Google Plugin and Superfish Menu.

I also created a fresh slave site and when I log into the administrator side of the slave site, I can only see the Superfish Menu module available. Both JCE and the Google Plugin are not available.

What should I do?

Normally, when you create a fresh slave site, you have nothing installed in the slave site.
This is like a new joomla installation.

So I don't know if you have created a fresh slave site as presented in the tutorial video 9 or CP-02 or CP-04 (I suppose YES).
If this is a fresh slave site, I don't understand why the Superfish Menu module is available.

Normaly none of them should be present when you create a fresh slave site.
So would you please send us the Superfish menu to our email present in our contact us
www.jms2win.com/contact

To install extension in a slave site, you can either re-install them with the back-end of the slave site or replicate a website that have this extension pre-installed or use the JMS tools that has the description of a limited number of extensions.
To know which are the extension defined for the JMS tools, you can click on the "tools" help button and that you can also see www.jms2win.com/component/content/article/135

I followed CP-04 tutorial in creating the fresh slave site. After creating it, I clicked on the site link and it took me to the installation of Joomla.

Everything went fine.

I then went back to the master and installed Superfish menu, JCE and google plugin in the master itself. And when I went back to the slave, I can see Superfish menu in the modules but not JCE or google plugin.

Does this mean I have to install them manually into each slave site? I would like my slaves to have the extensions available in the master.

I think I have found the solution. I went to tools and selected install from master or define from master and both JCE and Google Plugin are available now in my slave.

But there is no option for superfish menu although how that got automatically installed in the slave, I do not know.

Superfish is not yet defined in JMS tools.
As explained, this tools is only available for a limited number of extensions.
This is the reason why I have asked you to send this extension for a review and potentially add it in a next release of JMS patches definitions.