I have a 70 amp sub panel. I'm trying to figure out how to wire in a 40amp breaker in the sub from the panel in my house. I have two hot wires coming in to separate lugs, one neutral, but the breaker itself has one trip/reset lever yet has two screws on the bottom of the breaker;one on each side. Is this separating the 40amps into two 20 amp feeds?I want to wire up a device that requires 40 amps @120 and has a total of three wires;one hot ,one neutral,one ground. Do I need a different breaker or is there a simple way to
Solve this issue?

OK well I am going to give an answer, but I may need more explaining on your part as to what exactly you are trying to hook up.

The first thing I can tell is that you have a two pole breaker and trying to hook up a device with only one hot. Two pole breakers are for device that require two hots, such as red and black, like on some AC units.

So my advice, off what you posted is to go get a new breaker. A single pole 40 amp breaker.