Lots of help needed here
First off, those brake levers are not intended to be used by themselves. They are designed to be used inline with a set of regular brakes levers. The spot where you have the cable end is where a piece of housing should go. You also have the lever facing the wrong direction. The lever should be rotated so that you pull the lever towards to brake, rather than push (hopefully this is stating the obvious).
You are definitely missing the pinch bolt at the brake caliper too. Seeing the top tube wrapped in some sort of packing material makes me think that this is a brand new bike. Have you unpacked everything?
Honestly, my first thought is that you should immediately take this project to a bike shop and let them complete the assembly for you. You can study it and learn what they did and on your next bike, or when it comes time to replace some stuff, do it yourself. At the moment, you appear way in over your head. With a lot of effort on your part, you can figure this out but it will likely cost you a lot of time and potentially some money to replace ruined parts.