POST request

A friend of mine sent me this link:
http://www.thisislegal.com/challenge/p1

After a lot of try and error I came up with this

It`s far from the ideal as I failed to make a HTTP request with the
“secret code” parameter.

Any advide on how to do this?

Don’t post links to spam bot sites that you need to join to see the
challenge. If you are unable to comprehend the intricacies of copy and
paste, then you need to take a few steps back and conquer that challenge
first.