He’s suggesting that you advertise in local print media (which could be newspapers, magazines, phsyical bulletin boards, etc).
I’d give you specific help but your website isn’t resolving (getting an error over here).
I suggest that you look at what Craigslist did. It started very locally and saturated itself with local listings. Then it gradually branches out to other locations, getting saturated with each one. Now it’s a global classifieds board as you well know.
It’s not a bad idea. People aren’t going to list or view your classifieds if you don’t have an audience or listing traffic. Getting listings from all over the place with an scattered audience isn’t enticing at all. Focus on getting your current city using it. Once again I can’t see your website so I’m just taking blind assumptions.
If you can get your current city using it, surrounding areas have an incentive to join. And then THEIR surrounding areas have an incentive to join.
If you decide to go down this route, your question then effectively becomes “How do I promote this locally” which is much less daunting than “How do I promote this generally.”