Separate litter trays if you use them, and feeding areas. Be prepared for fisticuffs. They may get along fine, they may just tolerate each other, they may want to kill each other. We’ve done it twice, the first time was more successful, they would share a bed, second time was ok but they would regularly have a pop at each other (male and female) down to one again, and she’s much happier on her own – stalwart of a cat, outlived two males!