Working with Controls in MVVM

From the tutorials I've read on MVVM, I have learned that I can use a Command as a replacement for the click event that is commonly used with code-behind and also used with WinForms. In my application, I have a ComboBox, a TextBlock, and 2 checkboxes (within a GroupBox). I know that I need to use databinding in order to set the content of the controls. How would I access these controls in the ViewModel so that I can assign their content to the properties I've created in my Models?

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-- Tyler Hughes