How to set up Progress Sync? Unable to register

How do I set up Progress Sync? I want to sync reading progress with my Android device.

According to https://github.com/koreader/koreader/wiki/Progress-sync , you're supposed to 'create an account on one device by using the plugin's "Register/Login" menu.'.

But I am unable to find the Register/Login menu. Can anyone tell me where it is? I have looked at http://koreader.rocks/koreader-user-guide.pdf and there's no mention of where the register or login menu is.

Thanks!