Small potatoe of wordpress theme tutorial? if it is you, then thanks for that great tutorial Hello by the way
there are a few ways, this is probably the best. you can also do link exchanges and stuff like that but I'd rather run ads make a bunch of fake spammer accounts. they won't last more than a day or two, but you can do a lot of good spamming with 10 accounts. find all the groups that are relevant to your app on Facebook, and maybe some that aren't make posts with links to your app in them. watch your app grow. that's it! peace