SQL & PL/SQL :: Initialization Of Varray Variable?

1.)different ways to initialize a varray variable. one way i know is

declare
type nt_type is varray(4) of numer;
nt nt_type:=nt_type();
begin
...
..
...
end;

2.)is it possible to initialize a varray variable in begin section.

3.)
decalre
type nt_type is varray(4) of number;
nt nt_type;
begin
null;
end;

in this situation if i want to initialize a varray variable "nt" in separate stmt how to do it and where to write it?