When you enter your email, Google or Facebook account to log into the app, a registration link is automatically sent to your corresponding email inbox. By clicking this link, you are signing into the app.
Please note, that your email inbox has to be accessible on your smartphone via the system's email program for the registration link to work correctly. If this is not working, you can open the email on your laptop or computer and you will receive a QR code that you can scan with your smartphone to log into the app.