There are 2 different loans you can get. There is a Flex Loan you can get now before you file your 2025 return or the Refund Advance based on your 2025 tax return.
The Refund Advance usually starts in January and just when you are ready to file. And only if they offered it to you. You can't self select it. Then you don't get it until AFTER your efile is Accepted by the IRS which is usually late January. https://turbotax.intuit.com/refund-advance