You can just drag the sword onto one of the slots. Let me know if that solves your issue!
That wasn't working for me at first, not to sure why but I tried it again on a fresh action bar and it worked fine. Silly me. Ran for about 3-4 hours total today with manual breaks & seems to be running a treat.
Every now and again it seems to get stuck and just spin the camera around, not sure if anyone else has experienced this?