For some reason, folks like to argue about buffers. In my experience they do not cause malfuctions and subjectively make the gun feel like it is softer-shooting. Nobody has done a 100,000 round head-to-head, buffer vs. no buffer durability test, so how well they work is tough to say. I'd put them in the "no harm, maybe good" category.
You just take the spring off the rod, slide the buffer on, then put the spring back on top of the buffer.
In my experience, the Wilson buffers are no good, however. The ones made by CP or Heitt are a better product.