question

That is literally the million dollar question, isn't it? :)

There are many articles and books on both player acquisition and monetization such as this one, talking about the book Free 2 Play (http://venturebeat.com/2013/07/03/top-five-tips-for-making-money-from-free-to-play-games/).

As a base, acquiring players comes down to marketing - both the (relatively) free kind, building up your community through word of mouth, and the paid kind, with ads. Depending on the specifics of your game, your options are going to vary quite a lot:

• Is it a Steam game? Are you doing a Kickstarter campaign? In both cases, it's important that you be active on your game's page, updating it with fresh information, being involved in discussions with your community, etc.
• Is it a mobile game? Who are you working with on the platform team? If you have a strong relationship with them, it may be easier to get your title in front of the right people, to be considered for a feature.
• Is it a web game? Are you working with one of the major web game sites, like Kongregate?
• Do you have a publisher? They'll also have marketing channels you can take advantage of, generally.

Since it sounds like you mean this is a free-to-play game though, don't discount the value of your non-paying users (who will almost certainly be the majority). Having a player who loves your game, and who is also very social - or even someone with an audience on YouTube, etc. - can be as valuable (and sometimes even more valuable) than a customer who buys an item or two in your game.