Using Mono Scope with Digital Camera

[keyplus90]

recently bought a lense from ebay which is called scope and it is like mono scope which fits in front of your camera. I have Nikon D50 digital camera. I have tried taking photo and although I can see the image through my viewfinder but when I take to photo it is almost blank. I am not very good at manual function and usually use automatic. What do I have to do to take photo. Thanks