To edit a Payment Term, hover your mouse over the Manage button in the header menu.
A drop down list will appear.
By selecting the option "Payment Terms", a new page will open up with a list of all your Company's Payment Terms.
On the very right hand side of each Payment Term, are three vertical dots. Once you select these dots, you are given the option to either edit or delete the Payment Term.
Select "edit" to edit the Payment Term.