Can someone please tell me how to add crontab job in erpnext self hosted?

As it states in the subject. I would like to add a job to crontab in erpnext v13 self hosted. I thought I had to open terminal and type:

crontab -e

when i do this, I get a file that opens in /tmp/crontab.mSzNpM/crontab

So after I add my job to the bottom of th efile and I exit, it asks me to save in the tmp folder, which doesn’t sound right.

What am I doing wrong?