WPF Custom TextBox How do I get Text into it?

Hi, I am learning WPF and I am trying to learn MVVM. I have a usercontrol which has a textbox and a textblock and I would like to know how to make it so when I use the usercontrol, I am able to set text in the textblock. I feel like I am close however missing something. I am not sure what to search on google to find an answer so here I am!

My current code is attached in the images!