These are the steps if you decide to delete your account and data associated with it (starting version 2.0.0).
1. Open the app and click on the "Account" entry in the side navigation.
2. Click on the "Settings" icon in the upper right corner.
3. Scroll down until you see the option "Delete account" and click on it.
3. Confirm your choice in the dialogue popping up.
That's it :-).
After a short grace period your account information will be permanently deleted and all your data will be gone. In case you want to restore your account after deletion, get in touch with support.