How do I add a user to Ubuntu Server, and limit that users WinSCP access to a specific folder?

Question

I want to add a user with limited permissions (this user will only be transferring files to a specific folder on my Ubuntu Server, using WinSCP). I want them to only be able to access one directory from WinSCP (/mnt/virtual/), and be able to modify everything inside of that directory.

To give some context on why I need this:

• Ubuntu Server is running Plex, serving media to nearby devices.
• New files are uploaded from Windows box on the other side of the house, from non-tech savvy user, which is why I need a simple solution such as WinSCP which allows the user to simply login, drag and drop new files. This is also why I need to set limited permissions to this user.

I'm not very advanced in the terminal, so any help will be greatly appreciated. Thank you.