Selecting a top value and storing it into a parameter

You need to define the colum that needs to order by then something like:
SELECT tmpColzer into tmp FROM (
SELECT tmpColzer, row_number() over(order by some_column) rn  FROM tecoTable
)
where rn=1

declare
tmp datatype;
begin
select tmpColzer into tmp from tecoTable where rownum = 1;
end;

Neither of these are working for me? I am getting some compile errors in both which I cannot resolve.

This looks like just one small part of what may be a bigger problem (or program).  What will this result be used for?  In Oracle, maybe you don't need to declare a parameter to hold a value, only to pass it to some other program or query.  But, we have no idea of what the big picture is here for you.  If you describe the bigger business problem, we may be able to help you solve it in a simpler way in Oracle.