To add an expense, navigate to Finance - Expenses and fill in the following required fields;
Date: The date of the supplier invoice
Supplier: The name of the supplier (must be in your People & Firms)
Account Code: The expense or cost of sale account to charge the expense
Description: A description of the product or service being purchased
Amount: The amount on the supplier invoice including GST
Tax: If the invoice includes sales tax, set the tax code to GST and check that the amount is correct
X-Ref Number: The invoice number from the Supplier (or other reference)
With everything entered, click Add to schedule the payment.
For more information, refer to the Ardex Premier User Guide - Accounts Payable in Ardex (Entering Supplier Invoices, pg. 5)