Steps

Open Credit/Debit Notes and click Credit Note for a customer, or Debit Note for a supplier.
Set the Date, enter the Party Name and write the Reason. Add the Party GSTIN, Original Invoice # and Original Invoice Date if you have them.
Choose the GST Type: CGST+SGST within your state, or IGST for another state.
Under Line Items, enter the Description, Qty, Rate and GST% for each line. Add Item adds another, and the totals update as you type.
Click Save Draft to finish later, or Save & Post to GL to post it to your books.
To find a note, use From, To, Type and Status, then click Filter. Open a note to Print it.

Good to know

Deleting a note also removes its entries from your books.

The number is made for you in a series: CN- for credit notes and DN- for debit notes.

Word	Meaning
GL	General Ledger, your books of account. A draft note is not in your books until it is posted.