i will put it in the simplist terms i can think of.
the positive terminals will either both be joined together for 12v so both + terminals will either join together or run both to the starter, or seperate for 24v with one + terminal going to the starter and the second + terminal going to the - of the other battery, its as simple as that.
the battery cable layout will show if its 12v or 24v.

i will take some phone pics tommorrow if it helps of 12v and 24v battery layouts ive got machines sitting here 12v and 24v.