C# addition operator overloading

I am trying to port some C# code to another language (C# is not my usual language).

I have a vector class (cpVect) that overrides the '+' operator twice:

    public static cpVect operator +(cpVect p1, cpVect p2)
    {
        return new cpVect(
            p1.x + p2.x,
            p1.y + p2.y
            );
    }

    public static cpVect operator +(cpVect p1)
    {
        return new cpVect(
            +p1.x,
            +p1.y
            );
    }

I can see that a new instance of cpVect is returned from both methods but I'm trying to figure out how one would call these methods in a code example (so I can make sure I'm porting them correctly). For instance, does the second method add p1 to the receiving cpVect?

v3 = v1 + v2   <-- does this call method one above?
v1 = v1 + v2   <-- does this call method two above?

Thanks