This verb means to put someone on board a ship, to cause to embark. In Acts 27:6, a centurion finds an Alexandrian ship sailing to Italy and "put us on board." The verb emphasizes the action of the centurion arranging passage and getting Paul and his companions onto the vessel. Classical usage includes putting troops on ships or setting dislocated joints (putting bones back in place). Here it's straightforward: facilitating embarkation for the voyage to Rome.