guys tanong lang, how do i update the GPS/navi ng fort natin?

model: 2013 4x2 Fortuner 2.5G AT
Toyota AVN_KIT 2013
Version GTK3-C8-R.2.16.21836
Software date: Nov. 15, 2012
Map version 2.4 (03/04/13)

nagbrowse ako sa navi system pero there's nothing that says about updating.. thanks!