Let's just say that you can't unless you do a lot of research and do everything the Ceaser Milan way. It is very difficult as they will have developed the habit of fighting with each other so you will need to persist for at least 4 months. This will be an absolute headache and you will have to nip everything in the bud very quickly by observing and recognising certain dog behaviours that will trigger a fight. If it is serious, like they may kill each other, it is better to just rehome one of them, ASAP! I also would not recommend you to adopt another dog unless you understand and practice dog leadership as a pack leader and show dominance from the first day.
I have not seen male dogs fight over female dogs, but more often, fight for territory as this really matters to dogs.
Neutering does not help so don't go down that route, unless you are able to identify which is the weaker male, and neuter/castrate that one, so that he becomes more submissive but this hardly works (perhaps 30% of the time) especially if it has become a habit.