How to attach sensor from gazebo database(.sdf) to urdf model?

Hi, In gazebo, there are already available models (insert tab) which you can simple insert in your scene. I am having trouble with using it with my urdf model. I want to add velodyne to my robot. But the problem is that i cannot do this as the model available is in .sdf format. I have tried adding it using this link information http://gazebosim.org/tutorials/?tut=add_laser but NO LUCK. - -- -- I have also tried this approach but i cannot add velodyne using this approach though i have added different sensors using the same underlying concept: http://gazebosim.org/tutorials?tut=ros_gzplugins I am using kinetic.