When you put a brake lever on if its not a style that can open up all the way you will have to take the grip off the side you want. Then loosen the allen bolt and slide the lever on thats how you get it on. To connect the brakes up take your straight cable and on the end there should be a cylindrical looking metal piece. Look at the bolts on the end of the lever and you should notice that they are hollow and have slits cut out in them aswell as the lever itself. Line all the slits up with the one on the lever and then you should also notice there is a whole on the lever where the cylindrical piece will fit into. Put the cylindrical piece in then drag the rest of the cable so it can fit in between the slits in the lever and the bolt. Then once its passed and it fits snug in you can tighten the bolts with the slit so the cable cant get out and it will also ease up on all the slack you should have when you pull the lever.
If you still have any questions ask away.