Basic Ball Lightning question...

[Plass]

Ok, I have read here that Ball Lightning is good, and I know it's the elemental Arrow attack

Ball Lightning Fire a Lightning arrow that electrocutes nearby enemies as it passes by for 65% of weapon damage.

But where the heck do you get the runestones? I am about 1/2 way thru act 2 and I have yet to see one of the things.

[yertle]

Runes are skill modifiers that become available at certain levels; you don't have to find anything. Ball lightning unlocks at lvl 24.

[Plass]

Ok gotcha - that's my problem then, I think i'm level 23.

Thanks!