Here's the Online documentation concerning collections.
The principle's this:-- declare a varray type:
TYPE <I>type_name</I> IS VARRAY(<I>size_limit</I>) OF <I>datatype</I>;
your_varray type_name; -- declare a variable of this type and initialize it.
Here's what I do when I need a varray. I declare a PL/SQL index by table (no upper bound and no need to initialize it):SQL> declare
  2    type tab_type is table of integer index by binary_integer;
  3    my_table tab_type;
  4  begin
  5    for i in 1..12
  6    loop
  7      my_table(i) := i*i;
  8    end loop;
  9    for j in 1..my_table.count
 10    loop
 11      dbms_output.put_line(my_table(j));
 12    end loop;
 13* end;
 14  /
1
4
9
16
25
36
49
64
81
100
121
144
PL/SQL procedure successfully completed.
SQL> 
MHE