My iphone got stolen how can i find it?

I don't have the find my iPhone app (i really do feel stupid for not) i need a way to find it because i'm freaking out! I'm a wreck and really really need to know how. Please Help ANY Way YOU CAN! I appreciate it. And thank you in advance

If you have iCloud you could just log into it and download Find My Iphone app from the AppStore on your computer then log onto iCloud and use the app in there.