LiveAgent is able to use Redis for storing several frequently accessed data types (sessions, settings cache). It helps to take some of the load off of the database, and improves overall responsiveness of the application.
All you need to do is install Redis, and point LiveAgent to Redis' location, and LiveAgent will start using it.
The LiveAgent application server needs phpredis PHP extension. You can check if your server already has it in PHP info.
To tell LiveAgent where it can find Redis, you need to add setting REDIS_DATA_HOSTS to the settings.php file in /accounts/ subfolder of LiveAgent installation folder.
Format of the setting is a comma separated list of IP_ADDRESS:PORT
REDIS_DATA_HOSTS=127.0.0.1:6379,or.any.other.ip:port