In auto mode, change the EV + or - setting by moving the camera to relatively darker or lighter areas until you get the aperture you want. Then lock the AEL (or half shutter) and re-position the camera to take the shot.
Alan is describing a very old way to use Aperture-priority automatic exposure, a method that's been around since the 1960's. It worked great with Nikons that used their 60/40 center-weighted light metering. Inside the viewfinder of Nikon SLRs and d-slrs is a 12mm-diameter, scribed circle on the viewfinder screen.
The long-time standard Nikon-brand center-weighted light metering worked like this: That 12mm scribed circle has the MAJORITY of the meter's sensitivity and "weight" or "bias" devoted to it, with the remaining 40% of the weighting or bias spread out, over the entire balance of the screen's real estate. In the F3, Nikon went to an even more strongly-weighted system, the 80%--20% system.
Using this kind of center-weighted system, it was/is easy to just aim the camera at "an area", and hold the shutter button halfway down to lock exposure. With more-modern, AF cameras, it became necessary to add a control, or two, to the camera, to separate AE lock from AF lock, and so on. But the way Alan is describing things works really well. If you want MORE exposure, swing the camera to a DARKER AREA. If you want to shoot for the brightest tones, swing the camera toward a BRIGHT area, and then press a button and the exposure is set, and held. No need to add-in Plus- or Minus- exposure compensation on any dial or menu.
This is a really fast, easy, convenient way to use Aperture priority automatic mode. I learned to use this system years ago, and with the cameras of that era that had a constantly-visible light meter needle, not LED's or LCD readouts, the visual up- and down- of the meter needle was really easy to interpret sort of out of the corner of the eye...needle low=dim, needle high=bright...