You want the HTTP path to the files, not the FTP paths. Use FTP to upload them, but reference their HTML paths.
Eg,

http://myisp.com/myname/mypic.jpg">.
Make sure you leave off the FTP. Your ISP might have a different format for what the HTTP path is vs. the FTP path, so if you need an example, go to someone elses page on that isp and check their paths.
The super simplest way, of course, is to not fully realize the path. Eg, if your images are in the same folder as your HTML, just say:

If it's in a subdirectory called 'images', just say:

Regards,
Chairboy