I installed osticket on a virtual machine with ubuntu server 16.04, where everything is working correctly.
the language is in English as shown in the image:
Now I want to change the language of the osticket from English to Portuguese, does anyone know how to do it?
You will need to download the language pack. Access the page link , then select the Language Packages tab, and below you will have a listing with several translation packages.
Then just download the language pack and upload phar to the include/i18n folder of your osTicket installation.
To download you can use WGET, like this:
wget http://osticket.com/sites/default/files/download/lang/pt_BR.phar
or transfer the file to the folder on Linux, so you can use WinSCP, from which to view the folders in linux and transfer through windows.