We will create a database named “osticket”

sudo mysql 
CREATE DATABASE osticket; 
CREATE USER 'osuser'@'localhost' IDENTIFIED BY 'your_password_here'; 
GRANT ALL ON osticket.* TO 'osuser'@'localhost' WITH GRANT OPTION; 
FLUSH PRIVILEGES; 
EXIT;

Download files:

wget https://github.com/osTicket/osTicket/archive/refs/tags/v1.17.3.tar.gz
tar -xvzf v1.17.3.tar.gz
sudo mv osTicket-1.17.3 /var/www/osTicket

Folder permission:

sudo chown -R www-data:www-data /var/www/osTicket/
sudo chmod -R 755 /var/www/osTicket/