To enter purchase invoices in CStore Essentials use the following steps:
Login to your CStore Essentials Account
Click on Grocery -> Purchases -> Invoices (Note: you can also get to invoices from Pricebook -> Purchasing -> Invoices)
Click on the "+" button on the top right to add a new invoice
Enter the invoice date, vendor name, payment details, Purchase amount, invoice number (optional) and click on Add Invoice.
Note: If you are paying by cash, either select pending/unpaid and pay from day report later or enter purhcase in the day report.