Focus Points

I have been reading Jeff Revell D3100 book, but through my view finder after changing some settings I have changed to single focus and thought that when looking through my view finder that the centre focus point would flash red when I'm focusing on a subject but it is always the one that is to the left?? Why is that and can I change it??

The dial around the "ok" button on back moves the focus point around.

Brilliant thanks cnyram I must have tried all other dials and never thought of that cheers have a good day