Most hosts offer a way to upload a file or two inside the control or admin panel.
Or inside a directory listing there is often a choice for upload a file.
If not, might I suggest to you a FREE FTP program? Core FTP Lite will do everything you need, and more.
And check out this page for some FTP information that may assist.I go into more detail on this thread, what FTP does and what settings you need. CSB specific stuff is towards the bottom of the page. Some people try to make them sound complicated, but in reality, the functions you need are very very easy to learn.
1) Set up a host in CSB (user name, password, address of website)
2) Connect to that site
3) Find your website files (they might be in a folder called public, public_html, www, web, or directly on the host) on one side of the screen. Your files on your computer in the other screen.
4) Drag the file from your computer to your website.