At the bottom right of each post (except your own) you'll see two icons, and
You can click these if you feel the post is deserving of reputation.
Reasons to vote up: Posts that are informative, helpful, for example if someone answered a question for you... or if you find a post witty/funny
Reasons to vote down: Any post that breaks the rules really, or is just unhelpful, spam, flaming etc.
lulzworthy = worthy of lulz. lulz = lolz. lolz = things that made you lol. So he was saying if a post is lulzworthy (makes you laugh) you could vote it up.
Hope that helped. And by the way if it did help, then this would be an example of a post you might give reputation for... of course I'm the admin here so I don't care/need it... but you can if you want