Create a subdirectory on your PC where you write your stuff, then upload it using FTP.
Here's a sample upload script
Google will find you plenty of other examples.
Your Control Panel -> Advanced section has a facility to password protect directories
Create a test entry there, then checkout the files it creates to see how easy it is to modify the .htpasswd file.
(Edit .htaccess and .htpasswd files with a non-formatting text editor, eg Notepad.)