SFTP, despite it's name is really nothing like traditional FTP, it's much closer to SSH and scp than it is FTP. Best way to think about SFTP is that it's SCP with directory browsing. If you have an ssh account on the server then you should already be able to use SFTP.
Using your SFTP client of choice login to sftp://gpl.openqm.com/ on port 19580 (the same as ssh) and enter the same username and password as you would to access ssh.
Voila! SFTP Access! You can now upload and download files from the server over SFTP.