It depends upon when you have all of your information coded correctly and ready to import. TurboTax will not prompt you to enter or import this information unless you have done it in the past. If that is the case, when you get to your input section where your Quicken information is used for, such as a self-employed business, you may be asked if you want to import then. But when you actually import the information is totally up to you. Just make sure you complete your return before the due date.
This link is for how to import but there are also some helpful instructions on assigning tax form lines in the link that might be useful for you.