while running a proc/func inside a package (public ones)
u have to run using packagename.procedurename(parameters)

if its function because it returns a value

do it like this in sqlplus

variable x datatype of returned value(size)

declare
:x := packagename.functionname(parameter);
end;
/
and then
to see what it has returned
print x
which will return the value.
hope this helps