B16A1 Oxygen Sensors Question

I am putting in a b16a1 in my 90 Integra, it has 1 oxygen sensor on the exhasut manifold (B18A), the stock b16a1 stock exhaust manifold has 2, which one should I use? If I should use the B18A one what should I do with the wires for the other sensor? Thanks alot!

Jan