I'm going to show you how i figured out how to get here, This is the path you will follow.
Step 1:
Position yourself here:
Step 2:
Ride up here, within distance to jump onto the ledge nearby.
Step 3:
Jump onto ledge, and ride around the corner.
Step 4:
This is the tricky part, and is a pretty hard wall jump. The way i do it, is by holding both mouse buttons(move forward) and pressing D, and jumping once i get my Feet stuck on the wall abit. It's all one motion.
Step 5:
You should have landed here, you now need to turn walk on (/) key by default, and slowly walk along the edge till you get near the end of it. Once you get to about the end, you need to turn Walk off, and try to hop over the little corner.
Step 6:
Just walk over!
You should now be up, congrats!
Let me know if there is anything i can do to make this more clear, thanks.