You can always log in to scroll.com using your email address and password, or you can request an email for a login link from the app under "setting up Scroll".
Or, if you're already logged in on a different phone or computer, you can go to scroll.com/setup and email yourself a setup link.
You can use Scroll in lots of apps, too! Check out more details here:
Note: iOS users need to have the Scroll app installed.