I’m not sure. I’ve tried introducing two sows, but never boars. But I’ll try to help. House them in separate cages. As many times as possible per day, take them out for floor time or lap time. Introduce them. Once you feel sure that they are friends, put them in the same cage.
Try getting your pig a companion either a few years younger or a few years older. Staggered ages will help them easily decide who gets to be dominant, with hopefully no fighting.
Maybe try to make a second floor to expand the cage? I hear you can also buy another one and connect the two. This option is most preferred, because the recommended cage size for two boars is 13 square feet. More room can also minimize fighting over space.