Open a new WPF windows using MVVM

Hi, I develope a new WPF application using MVVM. I added a new button on the parent window in order to open a new window (child). The child window contains a couple of textboxes and a submit button. How can i open the child window from the parent by hitting the button using MVVM (not code behind)?

Please keep in mind that the service i use to fetch/save data from/to the server is injected to my parent window.

Thanks.