Just a heads up, posting in the forum just to earn money is generally frowned upon.

To answer your question, cryptomaniac_xxx was likely referring to stuff like Signature Campaigns and bounties, which can be found in the Services section. In a nutshell, some service providers will offer you a certain amount for posting with a signature advertising them active on your profile. There are also plenty of people who sell goods and services for Bitcoin.

But yeah, campaigns/bounties are supposed to add incentive to your participation to the community, not the other way around. Spammers are typically blacklisted from joining or even outright banned from the forum, so do keep that in mind.