nompere2004, here are 2 options for you. The easiest is the 1st one.
Option 1: Internet Explorer
1) Open Internet Explorers (not Chrome or Firefox)
2) Press "Alt", and the menu bar with File, Edit, View, etc will show up
3) Go to View > Open FTP site in File Explorer
4) Drop the file in that folder (incoming)
Option 2: Filezilla
1) Download Filezilla Client (not the Server):
https://filezilla-project.org/2) Put ftp.avast.com in the "Host" box
3) Click "Quickconnect"
4) Drop the file into incoming