@Roberto Di Lorenzo: The usual ways are (1) Run

magic -rcfile $PDK_ROOT/sky130A/libs.tech/magic/sky130A.magicrc

, or else (2) copy that file

sky130A.magicrc

to the directory where you are doing layout, and rename it to

.magicrc

. It is preferred to use the startup script rather than to specify the technology, because the startup script does more than just load the technology file.