To use the reconciliation functions, you need to add or import your bank statements.
Once you have added a statement, click on the "Add Transaction" button or the "Import Transactions" button to add your statement transactions.
Click on the "Reconcile" button to view a list of statement transactions to reconcile against your income and expenses.

Click on the "i" icon on the right to view which income/expense is reconciled against that transaction.
Click on the "tick" icon to un-reconcile the transaction.