Monica is available as a 1-click install on Cloudron. For those unaware, Cloudron makes it easy to run web apps on your server and keep them up-to-date.
When you visit the app for the first time, you will be prompted to register a new account. Put in your email address and password and you will be logged into the app. This is the only account that has access unless you invite other people.
There is a demo available at https://my.demo.cloudron.io (username: cloudron password: cloudron)
The Cloudron package is developed here.