On the lens, that 0.46 to infinity is the distance that you're focusing at - 0.46 is something that's 46cm away, and infinity is something really far away. That's what you change when you twiddle the lens to sort the focus.
f/1.4 is the aperture, which you should be able to change on the camera. It's how wide the lens opens when you take the picture. Page 42 of this manual tells you how to do that:
www.nikonusa.com/pdf/manuals/dslr/D40X_en.pdf
The aperture is how wide the lens opens - a smaller number (e.g. f/1.4) has a bigger opening so more light gets through. A larger number (e.g. f/7.0, f/14) has a smaller opening so less light gets through. A smaller number gives a shallower depth of field (so the background is more out of focus).
In aperture priority mode, you choose the aperture, and the camera decides what shutter speed to use to let the right amount of light in so that the picture isn't too dark or too light. But, if the shutter is open for too long, you won't be able to hold the camera still and the picture will be blurred. In the evening/night, there is less light around and so the shutter speed gets longer.
Page 37 of the manual tells you how to change the ISO setting. ISO is related to image quality. A low ISO (e.g. 100) gives a good image quality, but needs a lot of light. A high ISO (e.g. 1600) gives more noise, but needs less light. You might be able to get non-blurry pictures by increasing the ISO setting when it's darker outside. Or, by resting your camera on something so that it doesn't shake as much.