If I put something as an Expense how do I change it to a Transfer?

Welcome and thanks for posting in the Community, Wendy131.

If you have manually created a bank transfer there is no way of changing it to an expense instead you can delete it and create an expense. 

If the bank transfer is added from the Banking page, you can undo it first. Once added back on the For review tab, you can change the transaction type from a bank transfer to expense. Let me guide you how. 

1. On Transactions tab, select Banking. 
2. On Categorised tab, find the transaction and select Undo. The transaction you undo will be moved to For review. 
3. On For review tab, find the transaction you undo.
4. Tick Categorise, and on Transaction type drop-down menu select Expense. 
5. Assign the correct details on the transaction and select Confirm.

Here's an article that helps in handling your banking transaction in QuickBooks Online: Categorise and match online bank transactions in QuickBooks Online.

If you need any more assistance please do not hesitate to reach back out to us again.