I assume that it is better to edit a new template file offline. I suggest to test changes like that in a local installation on a local server (XAMPP for example) and upload the tested version on the host ;=)
If you want to use a complete copy of the theme:
copy the complete folder, rename the folder and upload it to your themes folder.
You should modify the header of the template-files
Code:
/****************************************************
* @File: template.php
* @Package: GetSimple
* @Action: Innovation theme for the GetSimple 3.2.2. / for get-simple.de
*****************************************************/
in this example the @Action is changed to show that it is a modified version for the german website
it makes sense to add another template to the existing active theme.
In that case you can either download the template.php, modify it, rename it, modify the header and uploat it to the original folder
if you have no active FTP, you can, at least, take the content of the template-file: open it in the the theme editor, copy the complete content into a local file and modify, but you will need FTP to upload the new version to the online-theme-folder
Cheers, Connie