If you use the default Blizzard frames, then:

MultiBarBottomLeft - is the left horizontal bar, above the default bar.
MultiBarBottomRight - is the right horizontal bar, above your bags.

MultiBarRight and MultiBarLeft - are the extra vertical action bars, left vertical bar and right vertical bar.

Capitalization is important for the Bar and Button numbers, but doesn't matter for the /Click portion.

The master/spammed macro can be Alt 1, or 1 or whatever.
It will call other buttons, so by pressing this master macro, the other macros are being pushed too.
Then you put each of the spells or abilities you want, into macros on these bar/button positions.
And use commas as an artificial delay, until the spell/ability will be re-used.