If you want to grow a jungle tree like they appear in the wild, place them on the ground in a 2x2 grid and then use bonemeal.
There seems to be two basic types a shorter and taller version. Anecdotally, it seems like the taller version is more common. Around spawn, when I got a shorter one, I'd climb up and plant another on top of it.
Also, single sapling jungle trees can grow right next to each other. So you could plant 30 in a line and make a giant living wall.