There is an option of "Install New Module" that you can use for this purpose. you need to have a package zip file to install or upload a new module.

Thanks, Paul. I've switched on edit mode and I've got more options now, but there isn't the 'upload new module' option, I was looking for. I tried using 'install module', but I get this message: A critical error has occurred. Could not find file 'C:\Inetpub\vhosts\whatcauses.com\httpdocs\Install\Temp\ys1wstxe\ReZults.dnn'. I'm guessing this option is just for installing modules, already on the server? I tried with the extension wizard as well, but I got the message that the file extension was invalid each time. Very confused as I can't seem to find the same options that are described in the tutorials.