Add TextBox

This macro will add a TextBox to the active Word document:

Sub AddTextBox()
ActiveDocument.Shapes.AddTextBox Orientation:=msoTextOrientationHorizontal, Left:=1, Top:=1, Width:=300, Height:=100
End Sub

Delete TextBox

This VBA macro will delete the first TextBox in the active document:

Sub DeleteTextBox()
'deletes first text box in activedoc
'not straithforward because its not easy to identify text boxes
    Dim oShape As Shape
    If ActiveDocument.Shapes.Count > 0 Then
        For Each oShape In ActiveDocument.Shapes
            If oShape.AutoShapeType = msoShapeRectangle Then 'we need to check both if oShape is of type msoShapeRectangle and its textframe contains place for writing
                If oShape.TextFrame.HasText = True Then
                    oShape.Delete
                End If
            End If
        Next oShape
    End If
End Sub

Write in TextBox

This Word macro uses similar methodology to write to the first TextBox in the active document:

Sub WriteInTextBox()
'writes into first text box in active doc
Dim oShape As Shape
    If ActiveDocument.Shapes.Count > 0 Then
        For Each oShape In ActiveDocument.Shapes
            If oShape.AutoShapeType = msoShapeRectangle Then 'we need to check both if oShape is of type msoShapeRectangle and its textframe contains place for writing
                If oShape.TextFrame.HasText = True Then
                    oShape.TextFrame.TextRange.InsertAfter "https://www.automateexcel.com/vba-code-library"
                    Exit For 'we just want to write into first textbox
                End If
            End If
        Next oShape
    End If
End Sub