If we are talking about a Heater Relay Board, (HRB) then look in the box it was shipped in: there are complete instructions.
But the thing you mentioned: one more connector is wrong: there are TWO more connectors. One is in the block along with the others, and you must notice that the numbers are different: 1, the H1, then 2, 3, 4, 5. The H1 is one of the two terminals for the heater. The other, H2, is off on it's own to the left of the power block.
HTH