Ko propo esprit 2 no reverse

[Br4d1ey131]

So, I recently purchased this ko radio and I love it! But, I cannot seem to find how to get reverse on the throttle. I've tried calibrating my speedo and trying it in different cars but nothing. Even when I plug the servo into the they'll ever channel it'll only go one way. I've read the manual but it's all very confusing, any help would be greatly appreciated!