Summarize:

Navigate to the Earn page, and browse the list of apps. If you find an app that you want to try, click on it to check how many points it offers. Then, click "Download" to go to the store page and download your first app! Bear in mind that it may take a day or two for Feature Points to credit you with the points that you've earned for a given app. You may not get points if you've downloaded the app before, or if you fail to complete the app's tutorial. Once the two minutes are up, you can close the app and return to Feature Points to download another app. Keep downloading and using apps in order to generate a steady flow of reward points. Set a goal for yourself: aim for a specific number of points, or play with Feature Points for half an hour to try it out.  Make sure that you are connected to WiFi, if possible. Downloading a lot of apps with your data plan can max out your data very quickly. Feel free to delete apps from your device after you've earned your points. At a certain point, you will fill up your device memory if you keep downloading new apps without deleting the old apps.
Select an app. Use the app for at least two minutes to earn points. Download more apps.