To edit the crontab you enter

crontab -e

Be aware editing the crontab in /etc/crontab with any editor will not activate the changes until you reboot the system. This is the reason to modify it with crontab -e. By default the vi editor is used (not my favorit).

Change to your current userdirectory. Just enter: cd

edit the file .basch_profile  (add the following line)
export EDITOR=/usr/bin/nano