If you’re doing a Discobot tutorial:
When you get to the message asking you to perform a Search for ‘Capybara’ you need to tick the ‘search this topic’ box.
That will give you 1 search result (a copy of the first Discobot tutorial message, but this time with an image of a capybara in it).
Reply to that post with a 
and you’ll get the certificate. 
If you fluff it up and it dead ends on you just ask him for a new one. 
More info: Discobot Tutorials
If you’re playing a word game:
No idea