Issue to switch J101 Nano boot from SD back to EMMC

I followed SEEED Studio instructions to successfully boot J101 from SD drive (J1010 Boot From SD Card | Seeed Studio Wiki). However, It is not possible to edit the extlinux.conf file in order to change the configuration back to EMMC, due to file owner given as ‘root’ and not possible to change permissions. Please how can I change this?