Where is the current signal?

Nowadays, the current sensor is usually integrated into the ESC and the current data is transferred to the flight controller throw the 'CURRENT'( or 'CURR' / 'CUR' /'C') signal. It can also be integrated into the AIO flight controllers. Take the SpeedyBee F7 V3 stack as an example, the current sensor is integrated into the ESC and is output from to the flight controller through the 'C' pin:

What are the correct settings for the current sensor?

The Scale value and the Offset value are the two key values for the current sensor. They should be set correctly in the Betaflight configurator(or the SpeedyBee app) due to the ESC's description/manual. In another word, different ESC should be set with different scale and offset values.

For example, for our latest SpeedyBee BL32 50A ESC, the values are:

How to calibrate the current sensor?

If the current draw is not accurate, you may calibrate it by referring to Pawel's informative video:

https://youtu.be/Zx5jmft1mp0

Or Oscar Liang's article:

https://oscarliang.com/current-sensor-calibration/