Registration and logging in, are two basic measures, that allow you to start using the app. By registering you’re setting up your account, which will later allow you to log in, once the account is created.
You’ll have two options: to register with Facebook, by clicking on „Sign in with Facebook”, or with an email address („Sign up with email”). If you choose the second option, the app will take you through several screens, where you’ll have to fill out some basic details about yourself (you don’t need to provide the city you live in and your weight, the app will set your weight to 75 kg by default). You’ll be asked for permission to contact you and send you information about the attractive features of the app.
If you already have an account, the only thing you’ll have to do is to click on the blue „Sign in” button, that will redirect you to the signing in screen. Here, you’ll have to sign in with Facebook or using the email you originally registered with.