You basically have 3 options depending on what tools you have access to:
1) Use a hydraulic press and push the bushing with the bolt stuck in it out. This is what I did, but not everybody has access to a press. My friend works at a machine shop, so he could do this for me. This is probably the easiest way.
2) Torch those bad boys out if you have a torch and some time to waste. I'm not sure if this is a good option or not as I didn't try it.
3) Drill the bolt out. However, this is easier said than done. I tried drilling mine out for a couple hours without really getting anywhere except screwing up bits. The bolts inside are really strong and don't drill too easily.
Options that will not work:
1) Pushing/pounding/punching the bushing out. I tried this, and that thing is really really stuck in there. Don't waste your time.
2) Welding a nut onto the broken off bolt in hopes of backing the bolt out of the bushing. I tried this also, the welds busted quickly.
Or:
If you ordered new arms with bushings already in them, that would solve the problem pretty easily.
Hope I can help out with my experience in dealing with the same problem. Like I said, I pressed the bushings out and just pressed new ones in, but you do have multiple options. Good luck working it all out.