As I stated before, they are on TOP of the wall, 80 feet above you. The gates are located on opposite ends, so you will have to circle around to the northern side to the main gate. There are small entrance doors at the bottom of each wall-tower for soldiers, but they are thick with 5-inch wood and have full iron hinges, locks, handle, and even vertical iron bars that lock the door, 2 inches thick.
also, keep in mind that between the inner wall and the outer wall, is the actual city around the castle. There's a mile between the inner and outer wall, further proving the accuracy and deadliness of the archers. also, remember that in the central tower of the main castle, there are also archers who are shooting explosive arrows, so yea. Talin and Drevo will have to be quick and discreet. as i told cuddles earlier, you will also have to be quiet enough as well. if what you do is too loud over the explosions, the archers will immediately know you're there.