On the left side of the camera near the base of the lens is the auto focus/manual switch...
Press the button in the center and turn the rear command dial and select AF-C or AF-S
(shown in top LCD)... Then while still holding the button turn the front command dial and
select single focus point (shown in top LCD) then release the button at the base of the
On the back of the camera is a lever with an "L" and a dot... Flip it to point to the dot
then press the "OK" button in the center of the menu navigation wheel to move the
focus point to center then flip the lever back to "L" to lock it in place... You can also
use the navigation wheel to move the focus point around when the lever is pointing
to the dot if you'd like...
I've learned with my D7000 that, more than with any other camera I've owned, reading the manual cover to cover (and keeping it in my bag!) is essential. Last night shooting the moon, I couldn't figure out how to do time lapse. Thankfully, I had the manual in my bag and could find out.