If you have the Qlik Web Connectors installed and running correctly (either as a service or standalone) you can get to the web interface for it at http://localhost:5555/ or http://machinename:5555/ if you are connecting from another machine.
From here you can pick the Standard connectors and then the SFTP connector. Using the GUI in the web page you can then input the details for the FTP site you are connecting to and download or directly access files from the SFTP server.
Once you have got to the data you need in the browser you can click the Qlik Sense tab and you can copy and paste the code to connect to the SFTP server. You will find some notes here also about Standard Mode - whcih you should definitely read.
Hope that helps.