Ensure that both are spayed. A bond with hormonal rabbits rarely goes well. Introduce first in a small, neutral area. Small initially is recommended because otherwise they will likely just sit at opposite ends ignoring each other. You need to get them to interact. Don't keep separating them, once they are together watch them for about 24-48 hours. Don't intervene unless it gets nasty. Circling usually means a fight is about to start. Nipping and chasing is natural though.
That's the basics I think, I may have forgotten something.