I will assume that you have created the DataSet, and that it contains one or more DataTables. You would normally use bound controls to display the contents of the dataset ie..(textboxs, labels, comboboxs, datagrids, etc). In general you would navigate to a desired value and set the variable to the value displayed in the bound control.
Are you asking how to set the variable to a field in a table of a dataset? How do you determine which record to set it to. DataBinding is what you want. The variable can easily be set to the value contained in the bound control.
Dim Variable1 As String = TextBox1.Text
Dim Variable2 As Decimal = Convert.ToDecimal(TextBox1.Text)
I'm not sure if that is the kind of help you are looking for, let me know.