From your dashboard:
- Click on the three little dots top-right of the bank account block and select 'Account Transactions'
- Find your transaction in the list - use the Search function to narrow down the entries if needed
- Click on the transaction, and from the 'Options' towards the top, select 'Edit' and update the account code
- Click on 'Save', and you're sorted
You may be looking at one of Xero's reports and come across the incorrect transaction. If the figure is in blue, follow steps 3 and 4 above - you probably don't need to go back to your dashboard to make the change.
Making changes via the dashboard is always an option if you become stuck.