To update just open Octopi and select system upgrade from the File menu, or you can use the folloing command in Yakuake or Konsole: sudo pacman -Syu
A system restart may be required after this update/upgrade. Remember to always take note of any pacnew, pacsave or pacoriginal file warnings during the update process, then compare and merge any differences that may be required prior to restarting your systems.
During regular system updates, the installed kernels will get updated within their series only (3.14.13 -> 3.14.14, etc.), Manjaro allows you to have more than one kernel installed at a time.