I spent a few hours with the Pi Scan to understand its structure and how the read only system works
To make it writeable
sudo mount -o rw,remount /
The files written to the PI will be lost on every reboot as the main folders are overwritten. Example of the etc folder to mount the overlay to the main folders.
umount etc/ mount etc_org/ etc/
Create a partition & make it writable
To make a part of the PI writable, I created a 3rd partition and mounted it in fstab.