I would like station a hero in barracks, not into the truck but in the barrack but when I click, the..

Which hero do you have that you want to station?

You cannot station heroes into the barracks buildings. There are combat Heroes (the trickster is one) which can bee added to the APC's to fight. There are development heroes that affect training of troops which are stationed in the training buildings for each type. But no heroes for the barracks buildings themselves.