First, you want to log data without closed loop fuel control enabled. Then in M1 Tune select a cell in the effeciency table where the engine was a steady state (or close) and use the "L" key (this is the Lambda Was feature). This will allow you to specify the measured Lambda and the target Lambda, and will make the necessary correction to the Effeciency Table to hit the target.
If you can run the car with the laptop attached, you can pause the live readings (Press "T"), and back up. With the cursor in the data graph and the middle of a cell selected. With the VE table active, press the "Q" key, and it will do the Quick Lambda function using the current data to correct the current cell - this even works with Closed Loop Fuel control enabled.
If you are on HP Academy, there is a webinar that shows this:
https://www.hpacademy.com/previous-webi ... -motec-m1/