There are couple of ways you can do this. The simplest one is as follows.
Go to Properties of the chart -> Sorting - > Drag and Drop Region field on 1st position -> Click on the drop down and Deselect the Auto sorting option -> Once you do this an option will be enabled which says "Sort by Expression" -> Click on the checkbox and write below if statement.
If(Region = 'North', 1,
If(Region = 'East', 2,
If(Region = 'West', 3,
If(Region = 'South(News)', 4))))
And check on Sort "Ascending".