NUnit Testing - Need Help

Hi
I am attempting to NUNIT test a method that takes 2 input paramters
a Point object
a Line object
The objects are from a outside dll, that is from a external vendor.
the class is as below

Code:

---

// Separate dll
 public class Line
 {

 public PointA
 { get; }
 public PointB
 { get; }
 protected internal Line() // Constructor
 public SetPoint(Point start, Point end)
 {

 }
 }

---

How can I instantiate the Line object from another solution not in the same assembly
in my unit tests ? And Populate the Properties ?