What setting should my Nikon d5100 be on to take pictures of Christmas lights?

What setting should my Nikon d5100 be on to take pictures of Christmas lights?

Start by using the cameras fine light meter.

Make adjustments based upon what you see on the cameras LCD

I use a tripod because you're going to do time exposure. I always use my camera's self timer at
10-seconds to prevent blur from me pressing the shutter release.

For lights at night I normally set my ISO at 100, my aperture at f/10 because that gives you far more sharpness of the actual lights than does a wide open shutter.So, setting on aperture priority at f/10 the camera will decide what your shutter speed should be and it'll work very well.It'll be longer and shorter for different lighting situations but what I've given you is a pretty good rule of thumb.

Here's a bokeh I did in the camera's program mode. In other words I let the camera decide shutter speed and aperture. That also works pretty well.

See the knob on the top right? Turn it to " scene ". Then right below there's another knob that's all black. Rotate that counter-clock wise and you'll see different thumb-nail photos. Pick the one that's closest to your lighting situation. The camera will do all the work for you.