Tutorial or help installing os ticket

Process failed by:

WARNING: The following packages cannot be authenticated! libssl1.1 php5.6-common php5.6-json php5.6-opcache php5.6-readline php5.6-cli libapache2-mod-php5.6 libargon2-0 libsodium18 php7.2-common php7.2-json php7.2-opcache php7.2-readline php7.2-cli php7.2-phpdbg php-apcu php-apcu-bc php5.6-xml php-pear php-gettext php-xdebug php5.6 php5.6-gd php5.6-imap php5.6-intl php5.6-mbstring php5.6-mysql E: There were unauthenticated packages and -y was used without --allow-unauthenticated

I took a look on OSTicket and it seems pretty easy to install. Personaly i always seting up my own webserver without using any pre-configured packages. If you need further information let me know!

Installing OSTicket shouldn’t be too hard: simply extract the archive (<a href=“http://osticket.com/download”>http://osticket.com/download</a>) in /var/www and run the installation wizard. <br> <br>This article explains it in more detail: <a href=“http://www.linux.com/learn/tutorials/318061-osticket-help-desk-ticketing-system-right”>http://www.linux.com/learn/tutorials/318061-osticket-help-desk-ticketing-system-right</a>.