Changes

Add the command line you want to execute at the end of the file that reads like this:

1. '''@reboot python /home/pi/x-c1/fan.py''' is a sample command, You '''MUST''' to modify it according to your needs.

Save and exit (CTRK + O and ENTER to save it). In nano editor, you do that by hitting CTRL + X, answering Y and hitting Enter when prompted.

sudo crontab -e