Realtime Database Rules and Re-Activation

I have been emailed that it has been deactivated due to rules not being safe enough, however Im not too sure what to actually write inside the rules.

My database needs to be visible for everyone. Only one person can write to the app which is the owner of the app, she can only write to it after she has put her password into the app, there is no sign in or login, its kind of my own rules inside the app.

What do I write inside the rules and how do I get the realtime database up and running again?

Thanks for your help.