Update 4 2 vertical scalar field

4-2-vertical-scalar-field.md

@@ -45,7 +45,7 @@ Double click the vertical _Color Bar_ on the right-hand side of _Rendering Pane_
 
 ##### 6. Control the size and location of the plane (optional).
 
-You can control the size and location of the plane by using _Rendering Pane_ only. To do this, you do :
+You can control the size and location of the plane by using _Rendering Pane_ only. To do this, you need to :
   1. switch from _Globe_ mode to _Map_ mode,
   2. double-click one of the corners of the plane, to reveal the control handles,
   3. drag the control handles to change the size and/or height.