A delivery challan is issued to acknowledge the delivery of goods to a party; it will result in decreasing the inventory stock. Once the party has acknowledged receipt of items the next step would be to issue an invoice.
Step 1: Please go to Income > Sales Order
Step 2: Select the Sales Order for which you need to Create a Delivery Challan.

Step 3: Click on Create Delivery Challan Tab. A new window will open up as below:

1) Select the Date
2) Add in Customer Notes.
3) You can mention the Terms & Conditions as applicable.
Step 4: Click on Generate. You can see the sample below.

Delivery Challans can always be accessed from the Sales Order.