little help please

I'm using a priority queue to organize some strings. However the queue put everything with the greatest weight at the top, and i'd like it at the bottom. My teacher says I should use a two arument boolian function, But I haven't the fainest clue on how to do it.

i don't have the code avaiable right now, but what i'm using right now looks a bit like this:

#iostream iostream
#include queue
#include functional

using namespace std;

int main()
{
priority_queue pq1;
....
....
and so on

thanks for any help