1) Pres SELECT + HOLD and rotate the switch to Ohm position. It should display
   000.0Ω. Now you can rotate the dial to choose what you want to calibrate. I
   will proceed with resistance measurement, but it works the same for volts /
   current / capacity / diode / temperature.
2) Now the display shows expected value on the input (0 for short, other
   quantities start with 30 or 300) Use thick, low resistance cable to short COM
   and V/Ω input (only for resistance calibration). 
3) Press SELECT + REL to get the meter ready. Let it read the offset, wait until
   the reading is stable. Press SELECT + RANGE to save the data. 
4) Now the display should display the next range (300Ω in case of resistance).
   Connect 300Ω resistor to the input and repeat step 3.
5) Once the desired quantities and ranges are calibrated switch the meter OFF.
   Adjustments will be made only for the quantities (AND RANGES!) which were
   altered and saved during the calibration process. It is possible to calibrate
   only one range of one quantity. Repeat step 1. Then press SELECT + HOLD to
   choose range (very touchy, it is easy to skip ranges so press the buttons as
   quickly as possible, don't hold pressed for too long). Now perform
   calibration as in steps 2. and 3. 
   
Credit: https://www.reddit.com/r/AskElectronics/comments/eydh16/comment/fggpit3/