migrate from FTP to SFTP

I am using following code for FTP in shell script file and it is working.I want to migrate from FTP to SFTP.What code changes/steps will I have to do for SFTP ?

FIN

ftp -in <<FIN
open $SAP_UP_SERVER
user $SAP_UP_USER $SAP_UP_PASSWORD
asc

put $PM00_OUTPUTS_DIRECTORY/$SAP_UP_FILE_CSV /$SAP_UP_FILE_CSV
prompt ... End File ftp dates transaction


quit
FIN