This is the chapter of the MemberManual that describes how to transfer files using scp and sftp.
You can use plain scp, but it overwrites destination files and is usually only applicable when you are uploading new files to HCoop. If you don't want that to happen, please use rsync:
scp -r ~/html/hcoop/* USER@ssh.hcoop.net:public_html
You can run command-line sftp (Secure FTP) tool:
sftp USER@ssh.hcoop.net Connecting to ssh.hcoop.net... Password: sftp> help
With GUI FTP clients, SFTP connection is possible if the clients support "Secure FTP" or similar as the connection method. In Unix/Gnome, you could use for example gftp; for KDE, use the sftp KIO slave (sftp://ssh.hcoop.net: in Konqueror or Dolphin); for Microsoft Windows, WinSCP is recommended.