Upgrade instructions are included in the release notes here:
The Server/Sensor versions included in the this release are:
Windows Sensor: 184.108.40.206026.0747
OS X Sensor: 220.127.116.11103.1147
Linux Sensor: 18.104.22.168131.1504
This patch release contains primarily bug fixes and stability improvements.
For more details, please check out the release notes: Carbon Black Response v5.2.6 - Release Notes. If you have any questions/concerns, please post back here or contact Carbon Black Technical Support following the standard process.