Printing payment terms in invoice

Trying to print payment terms in invoice.
Following codes not working. Any help please.
{{ doc.payment_schedule[0].description}}

I am NOT a programmer on any respectable level, so please check this properly as i can offer no guarantee at all…
You need to make sure that the referring docType contains/allows access to the relevant field

Thank you very much.
Selected doctype terms & conditions, looks like now it is working.