On which setting must the camera be for taking pictures as night

To obtain the best results, several factors must be taken into consideration. Traditionally, for taking pictures indoors the use of flash was mandatory, but nowadays with increased sensitivity in cameras, this can be largely dispensed with.
The first variable is the ISO rating - for indoor use by ambient light, this needs to be at lease 800, possibly as high as 2400 - as you have given no indication of the equipment used, all answers must be a little vague, giving guidelines rather than strict instructions.
Next is to adjust the White Balance - there will be various settings depending upon the type of lighting in use. Old-style lightbulbs are tungsten, whereas more modern tube lighting is fluorescent, and they possess different colour temperatures. Choose the one appropriate to the light source.
Finally, to ensure as much light as possible reaches the sensor, do not stop the lens down to more than f5.6.