How to promote classifieds site?

Welcome to the forums, @Mohammed_Khairulla.

The basics of promoting a site are the same whatever its nature. I’d suggest you download Google’s “Search Engine Optimization Starter Guide”, which will give you a good grounding.

You’ll also find a number of helpful threads on the forum here. A good place to start would be All You Need To Know About SEO. If you search the forum, or simply look through the Marketing section, you’ll find plenty of information.