Upload or Download by using FTP directly through your browser
Type the following in your browser address bar:
ftp://upload.comcast.net

( you also need your username and password )

Download by using Comcast FTP directly through your browser
Type the following in your browser address bar:
https://home.comcast.net/~[yourusername]/[yourfolder] {/[yourfilename]}
Most likely . . . . .
https://home.comcast.net/~[yourusername]/myfilelocker

I recommend using an FTP program like CUTE FTP, but this will do in a pinch.