well first off, id go read the
The OFFICIAL Community Guide to FPSC! , They have a nice article for publishing your games in there.
Secondly, id start up a thread about your game in the showcase section, to see what people think about it, and such. But as a warning to if you dont read the rules first (which you should) YOU MUST HAVE AT LEAST A SCREENSHOT BEFORE POSTING! other wise your thread will be locked.
other than that, usually the best advertising is word by mouth. And google ads, see if you can get google to host an ad for you, and go post your game on any of those Top 100 (or whatever) game ranking sites.
hope this helps