If you come from the Eclipse world, you should be lost because it's not very clear how to generate a release build version of an .apk file.
In this Android Studio tutorial, we are thus going to see how to resolve this release build generation.
First of all, click > Build > Make Project.
Then > Run > Run nameOfYourApp.
Your project should be built and of course in the debug version.
You can see this generation it in the following directory:
But what we want it's the release build of this .apk file.
Normally you could create the app-release-unsigned.apk file directly by building it in Debug mode.
And find it in the apk\ folder just described.
But if it doesn't work, you have to create this release file differently.
So to generate it, on the left side of the Android Studio, there is a Build Variants menu (maybe written vertically). Click it.
The Build Variants window tab has appeared, click debug and change it by release.
Rebuild your project application > Build > Rebuild Project.
Then click Run, a new window has appeared, click Run > Continue anyway > Choose the device you want to run with > OK.
The release build version of your .apk has been generated into the same directory as your debug ones:
You can note that the name is app-release-unsigned.apk and it was exactly what we wanted to have.
Free to you now to generate a signed application to upload it to the Google Play store.
And if you had still troubles generating the realease, let's try a last way that always work.
From your Android Studio > Build > Generated Signed APK... >enter all necessary data > Next > Finish.
If you don't know how to manage the keys, pick some information up in this API Google Maps tutorial.
This Android Studio is quite interesting to program Android application and is a serious rival to the classic Eclipse.
Good job, once again you've made it.