How does one do this in c#?

Let's say that myclass has :

private enum Days{};

1) How does one add data to the enum inside the myclass with the help of the constructor? As in :

myclass my = new myclass(Monday,Friday);

so that the enum inside the class gets the "Monday, Friday" properties.

2) Can one also make a property for an enume inside the class once it is initialized ? For example :

my.Days = new enum Days(Tuesday); //where the old settings are replaced.