When You click on "New Statement" a window will open
There you can see the list on journal items that are 'not reconciled'
There you can see the list on journal items that are 'not reconciled'
Fill the dates mentioned in bank statement in 'Bank.St Date' column of respective line. Click on 'Save' button before closing the window.
One more thing to point out is, this will also mark the bank payments as 'Reconciled'