auto update to HB ?

[Microeye]

hi

i have htc flyer and htc sensation xl, they are running GB...
and every time i check for update its says that the device is "up to date", and there are no available updates...
why its cant update automaticly ? (do i need to do something)

or is there a menual way, but an easy way? im not the smartest with those androinds
please help

thank you
CS