$ sudo apt-get update
$ sudo apt-get install libcsync-plugin-sftp 

libcsync-plugin-sftp is installed in your system.

Make ensure the libcsync-plugin-sftp package were installed using the commands given below,

$ sudo dpkg-query -l | grep libcsync-plugin-sftp *

You will get with libcsync-plugin-sftp package name, version, architecture and description in a table

libcsync-plugin-sftp package basic information: