FTP login with proftpd won't work.

You have multiple ways to do it. FTP is one of them, but not a recommended one. It’s not so secure, so better options would be SFTP (Secure FTP) or SCP (Secure Copy).

How To Use SFTP to Securely Transfer Files with a Remote Server will cover you if you use Linux and want to use SFTP.

If you use Windows, or just want to use Filezilla - How To Use Filezilla to Transfer and Manage Files Securely on your VPS will cover you. Anyways, I recommend you to read this one even if you are not using Filezilla. It explains difference between FTP, SFTP and SCP which can help you.

In case you want to go with SCP, on Linux you can use scp command. Basic syntax is: Upload to server:

scp -r /location-of-file-on-local/ server-user@droplet-ip:/remote-path/

Download from server:

scp -r server-user@droplet-ip:/remote-path/ /location-of-file-on-local/

On Windows, I found WinSCP to be best for it. You can manage files with it and it’s intuitive to use.

If you have more questions, feel free to ask. :)

Why are you using FTP instead of SFTP?