Accounts payable is part of accrual accounting for expenses.

A invoice from a supplier or vendor should be entered as a post in the accounting as a recognized expense.

Select type of expense

Now enter the data

After you click "Save", navigate to  the "Accounts Payable" tab. You see the transaction here as recognized expenses. 

Note: You can pay the bills from here. (click radio button). When you do pay the expense, the property journal will be updated with this transaction, and the bank balance will be reduced for the expenditure. 

Note: When you have paid the invoice the "Profit and Loss" will reflect that expenses as paid.