On the ribbon go to Accounts > Chequebook and add a Deposit.
Allocate this to a 8-2000 Bad debts recovered GL Account using tax code G.
Further information
Understanding Debits and Credits
Use Debtors and Creditors Adjustments
Clear the Historical Balancing Account
Suggested End Of Month Procedures
Enter Capital into the Business
Enter Government Support Payments
Enter Prepaid Expenses and Amortising Costs
Purchase a Capital Asset Under Finance
Record Debtors/Creditors Contras
Remove Duplicate Payments in Closed Period
ATO Reportable Sub-Contractor Payments
Share Utility Expenses with other Businesses
Variance in Trade Creditors and Creditor List Total