First, update the repositories and upgrade the system

apt get update
apt get upgrade

Install vsftpd Server

sudo apt install vsftpd

Start and enable the system

sudo systemctl start vsftpd 
sudo systemctl enable vsftpd
sudo systemctl status vsftpd

Create a FTP user

sudo useradd -m testuser 
sudo passwd testuser

Configure Firewall to allow traffic

sudo ufw allow 20/tcp 
sudo ufw allow 21/tcp

Change default FTP folder

sudo usermod -d /var/www/html ftp
sudo systemctl restart vsftpd.service

Allow users to authenticate

sudo nano /etc/vsftpd.conf

Search for write_enable=NO and change value to YES
Save the file and run

sudo systemctl restart vsftpd.service