To use this app you need a reMarkable paper tablet.
Get yours at www.remarkable.com
The reMarkable Companion for the reMarkable paper tablet is the perfect app to sync your content with other devices. It gives you easy access to all of your documents to view, organize and share.
Make sure you connect your reMarkable paper tablet to an account at my.remarkable.com before you sign in. You’ll need to use the same email or third party login for both your tablet and mobile app.