To take a dark frame you can simply cap your telescope and integrate using the same time that you are using for acquiring the raw image. The bias frame is an image made with an integration of zero seconds and shutter closed. It contains the amplifier zero-point offset, the random readout noise from the amplifier and the noise from camera electronics. It is an image of a uniform object such as twilight sky or a sheet of opal glass attached to the inside of the observatory dome.
Basic calibration is adequate for simple observing tasks.
Standard calibration corrects for vignetting and CCD nonuniformity, but constrains you to the same integration timr for your images and darks. Advanced calibration gives you the freedom to use different integration times for your images and provides superior dark subtraction via dark-frame matching. Individual dark and flat fielded frames or calibrated images can be added or averaged for better results.