Ensure you have the following:

Step 1: Click on Orders from the left menu > Click on "New order" > Standard.

Step 2: Enter the order header details.

Step 3: Enter a line item by clicking on the "Add Line Item" > Change to Add Manually

You can add as many lines as required.

Step 4: Enter line item details and click on "Add item" to save an item.

Step 5: Select the Budget against which this purchase is being made. [This is only applicable if you have budgets enabled]

Step 6: Click on "Submit" to submit an order for approval.