Nice .

Cal - Don't even have that camera on Auto for a second . Jump straight into "Av" mode (Aperture Priority) Moving the command wheel will allow you to set the aperture to what you want (giving you control over the Depth of Field) and holding down the Av button on the top of the camera and moving the dial will change the exposure bias.

Based on where you are shooting set the ISO to either 400 (For outside shooting) or pretty much max for inside shooting (I assume this will be 1600, although iirc using ISO booston a Nikon it is labelled as "High1/2/3" with "High3" being the max boost (This was on a D5000 though so may have a few more boosts over the D3100, principle should stay the same though ))

From there, just change the exposure bias to get the shot looking as it does for real, oh, and Make sure "VR" on your lens is set to On!


Oh, and above all, have fun!