The first thing you need to do, if you haven't done it already is you need to place the power supplies. Finding where they go can be a little bit tricky but we'll get you started. Any time that Juno stops you to talk, it means that you are going in the right direction.
From the Animus, turn towards the gate and find the building with the large staircase just to the left of it. You'll have to cross a gap to get up the stairs. Go up the stairs and into the next room to find a large room that looks like it uses a lot of power. On one side of this room will be stairs leading up. Go up the stairs and they will turn left. Just as soon as they turn left, they will stop abruptly. From here, turn and face the middle of the room. Between two of the columns, you can see a small metal beam. Jump onto that and climb up.
Follow the beam as it leads you across the center of the room. At the end of the beam, run up the wall to find another beam. Follow this beam and jump to the next. Run off of this beam to land back on solid ground. From here, turn right to find where you will find the first power source.
To place the second piece, start again at the animus facing the gate and turn right. Walk across to the section under the overhang. From here, turn right again and you'll find a small doorway in the wall. Walk through the doorway and go up the stairs you see in front of you. Follow the series of stairs as they lead you upwards. When you run out of stairs, turn left and then at the end, turn right.
You'll enter a large room with the spot for the power source across a large gap and next to Juno. You can't reach there directly so run along this platform and through the broken hallway. Keep going to the end and then turn right. Jump the gap and instead of going down the obvious stairs, turn right to find a small hallway with a ramp leading down. At the bottom, turn right and then go to the end and turn right again. As you go down this long hallway, watch on the right side for an open room. You can climb the wall at the back of this room and at the top you will be able to find Juno and the place for the power source.
The second power source will open access to the final location. From the Animus and facing the gate, go right once again. This time, find the stairs under the overhang. Follow this path as it leads you into the structure above. You'll enter a room with a bunch of half sized columns covered in ellow gemstone. Climb up the half pieces in the middle and then jump across to the half columns hanging in front of you. Slide left and then make your way over to the platform nearby.
Follow this path around and turn left. Jump down and swing across the poles here. At the end, you'll jump to another wall filled with Gemstones. Climb to the top and pull yourself up. Continue down this path, using the gemstones a guidelines for where to go. This will eventually take you to the final power station. Place this and you are ready to use the key if you have it.
