in the newer version of DobotStudio, you don't need the Sensor Calibration Board.
A small switch have to be enclose in the Dobot Box. It looks like this.
If you want to calibrate the sensor, go to Settings in the upper right corner of DobotStudio, choose Auto Levelling and follow the steps DobotStudio describes.
This procedure will take a short time, but the result will be the same as you would calibrate the Dobot with Manaul Levvelling and the Calibration Board.