To the UC_LoggingIn I've added an progressbar.
To the LoggingInViewModel I've added an property CurrentProgressValue which is bound to the progressBar in the view, I also added an method to listen for events from Serverhandler, specifically the OnChangedServerLoginProgress.
On ServerHandler and ServerWorker I've added events OnChangedServerLoginProgress, it works this way.

LoggingInViewModel listens on ServerHandler's OnChangedServerLoginProgress event.
ServerHandler is listening to the ServerWorker's OnChangedServerLoginProgress event.
The ServerWorker is firing the event each time it completes a part of the initialization/login procedure, sending N amount of points back to the listener, this means the ServerWorker knows how many steps there is to login so its basically Steps/100.
The LoggingInViewModel displays the current progress in its view's progressbar.