Well you have to first beat the 7th gym. them go to somewheere in the unavo region.
you use waterfall at the Pokemon waterfall or the battlefield.
Waterfall is an HM that, if taught to a Pokemon, allows you to climb up a waterfall.
U don't go through the waterfall, u go over the waterfall. The goal is to have the HM waterfall. This HM allows ur Pokemon to climb the waterfall.
one of your party Pokemon has to know waterfall press A on the waterfall it will say it's a waterfall do you want to use waterfall say yes and you will go up the waterfall
HM Waterfall can be found on Route 18 in Pokemon Black and White.
Most water type Pokemon can learn the move Waterfall.
squirtlewarturtleblastoisepsyduckgolduckpoliwagpoliwhirlpoliwrathtentacooltentacruelseeldewgonghorseaseadragoldeen seakingstaryustarmiegyradoselaprasvaporeonomanyteomasterkabutokabutopsmewchinchoulanturnmarillazumarillpolitoedquagsireslowkingqwillfishremoraidoctillareekingdrasuicune My Lapras and Gyrados Know the move waterfall
Most water Pokemon will learn waterfall i believe. For certain if you have PIPLUP, TENATACOOL, or TENTACRUEL, it will learn Waterfall. Hope I Helped!
Waterfall can be found on route 18
You get it from Juan in the Sootopolis Gym after beating him. Then, you get Waterfall.
HM05 Waterfall is found on Route 18.
You can find Waterfall in the Dark Cave.