Creating a new user in WinSCP version 5.7.5

Hi,
A vendor has created a SFTP server, and give me credentials to log into it. I want to create a few more users/passwords to be able to log in and upload files and download files. How would I go about doing this? This is running on Windows 7. Thanks.

You have to ask the vendor for that.
You cannot create users over SFTP protocol/WinSCP.