There might be a description in the relevant Erection Maintenance manual, which one of our American friends can possibly advise on. However, they work basically as I described earlier. Look at the pictures Joe posted of the B-24 bomb bay, and you will see the vertically-mounted beams.The shackles were mounted on these, horizontally, one above the other, with the relevant spaces for the bombs being loaded.
Each bomb was winched into position, and the bomb crew would use the two levers ('sticks' in the centre of each shackle arm, to close the jaws ('hooks') over the suspension lugs welded to the bomb casing. The arming wires were connected, from the aircraft's electrical circuit, to the bomb fuse train, and safety pins inserted, to prevent the impellors (small, propellor-like vanes) from turning.
Before the run-in to the target, the Engineer would go out onto the bomb bay catwalk and remove the pins from each bomb, thus 'arming' them. When the bombardier selected each rack, or perhaps the 'salvo' circuit, and pressed the bomb release, an electrical circuit would cause the sevrvo on each shackle to push against a detent, which opened the jaws, releasing the bomb(s).
As the bombs fell clear, the wires to the fuse chains, firmly attached to the vertical beams, pulled out of the fuses, which allowd the impellor to start spinning in the slipstream as the bomb fell, arming the fuse, which could be an impact fuse, timed fuse for air burst, or a delay fuse, the latter detonating the bomb minutes, hours or even days after it struck.
A fairly basic explanation, but hopefully it helps.