Instructions for TFTP server
https://help.ubuntu.com/community/TFTP
sudo apt update
sudo apt install tftpd-hpa
sudo service tftpd-hpa status
To copy your file to the TFTP server
cp YOURFILE /var/lib/tftpboot/
For Ubuntu 20.04.1
cp YOURFILE /srv/tftp/
Defaut config file for the TFTP server
vi /etc/default/tftpd-hpa