Detecting Collisions with Sphere Collider

Hey Guys,
I am trying to detect a collision with a sphere collider in my game, but am having a difficult time finding information on it. What I have is : A cylinder with an added “Sphere Collider” Component (added through the gui “Add component”). A block called “Unit” which is going to be colliding with the sphere collider. I am trying to make the sphere collider attached to the cylinder print a message when the block enters the collider field. I looked at the documentation and dont know what to do with the code:

public class Tower : MonoBehaviour
{
	// Update is called once per frame
		void Update ()
		{
		}

		void OnCollisionEnter(Collision col) {
			if(col.gameObject.name=="Unit"){
			Debug.Log(col.gameObject.name);
			}
		}
	}

Anything would help guys. Thanks,

@xortrox I actually solved it. I was wanting the ontriggerenter function and changing the parameters to collider! Thanks man,