John: Obviously if the brow tine on your deer is only a stub, or maybe 1 or 2 inches long, the only thing it can be used for, other than making buttons, would be a short handle for an awl, or something similar. On the more mature deer, brow tines- the ones inside the main beams that usually point forward, or inward towards each other- can be very long, and then can make good handles for knives.
If you are going to use it on a full tang blade, then its probably easiest to simply cut the antler in half on a saw, rout them out for the tang, half each side, and then epoxy and pin them to the tang. The other way is to drll a hole down the middle of the antler the entire length, which is often hard to do, because drill bits follow murphys law- if anything can go wrong, it will!- and will be either too short, or will find some way to drift off center during the drilling operation, etc. Drilling two hole to meet in the middle is even more fun! Since the tang is not likely to be round, but rather rectangular in shape, you will want to fill the space around the metal tang with epoxy to add strength to the antler handle, which is brittle, and can chip out on you. Then you have to make and fit your end cap, and put them all together to finish putting on the knife handle. Are we having fun, yet?