New melee player and confused by how Warcries and Endurance charges work

Really dumb question, I am a melee noob and am playing VFOS, do Enduring Cry and Infernal Cry have to hit mobs to gain the buffs and Endurance charges? I have my stat page open looking at Endurance Charges and it never seems to go up from 0. And if I leap into a pack to try to cast Enduring Cry directly on them I get destroyed before I can even do anything.

they need power to get buffs

monsters/bosses/rares give power

mastery gives some power regardless of enemy nearby