How to start REPL mode when connected to an Arduino Portenta H7

Who has a step by step explanation on how to do it ?

I can sucessfully run micropython scripts

It should do this over USB by default if you connect to its serial port that it appears as.

Do I need to set the REPL Flag in Settings?

No, it should just be on when you connect to the serial port. Make sure to set the DTR flag high.

Which Pin or Address is the DTR flag?

It’s in software. When you open the serial port over USB you need to make it high (false in this case because of inversion):