Others have already answered your question about the furigana, but am I understanding correctly that you’re trying to get into reading native content for the first time?
If so, Hunter x Hunter is unfortunately not a good choice for that. It’s one of the two hardest mangas (the other one being “Cells at Work!”) the ABBC every tried. In fact it’s so hard that it would belong in the Intermediate Manga Club. I’ve been reading Japanese for about 4 years and judging by it’s Natively level I’d still have a hard time with Hunter x Hunter.
I’d recommend choosing something easier from the list (look for low “Natively level”, ideally ~L18 or below).