Hi Manish,
You don't need to create a destination in the case of SOAP as a backend protocol. Your questions are answered in these blog: How to connect SOAP WebServices with Integration Gateway in SMP3 (use eclipse kepler instead of juno even the blog is done using juno). Writing Custom Script in SMP 3 Integration Gateway
Let me know if you have any other questions.
Regards, Midhun
SAP Customer Experience Group - CEG