It's very easy to track how your app is doing using Google Analytics. Here are step by step instructions for creating a new mobile app property in your Google Analytics account, and then adding your tracking code inside of your mobile app.
First, log into your Google Analytics account and select "Admin".
From the "Property" section, click the dropdown and choose "Create new property".
From here, select "Mobile app" as the property type, and fill in some information about your app.
Click "Get Tracking ID" at the bottom of the page. Your tracking ID will look something like "UA-xxxxxxx-yy". Copy this number, and log into your App Press account.
Paste your tracking ID into the project settings panel of your app project. You can find this by hovering over your app icon, and clicking on the gear that appears. Just paste in your Google Analytics ID, and you're all set!
Now you'll be able to see where your visitors come from, what screens are most popular, devices your users are using, and a ton of other great information to help you market and manage your mobile app.