The syslog-ng application is part of all major Linux distributions, and you can usually install syslog-ng from the official repositories. If you use just the core functionality of syslog-ng, use the package in your distribution repository (apt-get install syslog-ng), and you can stop reading here. However, if you want to use the features of newer syslog-ng versions (for example, send log messages to MQTT or Apache Kafka), you have to either compile the syslog-ng from source, or install it from unofficial repositories.