Read the manual. Very important.
Make sure your subject is well lighted. It's not always about adding more light. Sometimes, simply facing another direction works better.
Set camera to Auto mode. Take a shot. If too dark, increase EV (Exposure Value, Exposure Compensation, or AEB). If too bright, decrease EV. If hopelessly too dark even if the sun is above your heads, use flash.
If really, really, really dark, use flash. If too dark still with flash, step forward. If too bright, step back.
Now you know!