The OP is so vague as to be unworthy of proper, considered replies.

This sounds like an assignment of some sort, if so then all the necessary information (or details of where to obtain it) will be available to you in your course material.

If it is not an assignment, then why bother writing an app to do this. There's plenty of existing tools for exactly this purpose. Putty is a SSH client and as such is not specifically designed for file retrieval. WinSCP on the other hand is the ideal tool for this task.