If you already have content installed just download the template and all of the components and modules that go with it. You dont need to download the demo.
Then you would have to install the template and all of the modules manually. One of the easiest ways to do this is to install the demo in a sub directory. And switch back and forth between the two to copy the codes to your main website. Make sure you have your wysiwyg editor turned off so that you dont strip out the codes.
Also you would need to upload any image files that are being used to the main website.