An Inquiry into the Nature and Causes of the Wealth of Nations by Adam Smith is sort of a how-to, I guess. It's a description of why specialization and the division of labor, combined with free trade, lead to prosperity.

Another book of a similar title, The Wealth and Poverty of Nations: Why Some Are So Rich and Some So Poor by David S. Landes, is a prominent work in development economics and is more of a comparison of different institutions.

I think most economists would say the purpose of economics is to understand human behavior under conditions of scarcity. Most would probably add on something about informing wise public policy.