At what point do you apply for the advance loan? Why do I not have the option to apply for an advance? Do you have to submit the return first?

The advance has to be offered to you.  When you go through the FILE section you might see the option to click on Refund Advance.

https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-refund/offer-details-disclosures-refund-advance-program/L4ljXp6TI_US_en_US?uid=lrp7nbvp 

https://turbotax.intuit.com/refund-advance/

Refund Advance eligibility

Here are some of the eligibility requirements to qualify for a Refund Advance loan:

• You’re 18 or older
• Your expected federal refund amount is $500 or more
• You’re not a resident of North Carolina, Connecticut, or Illinois
• You’re e-filing your federal tax return with TurboTax
• Your physical address is listed on your tax return. Your address must be located in one of the eligible states and can’t be a PO box or prison address
• You’re not filing one of these tax forms: 1310, 4852, 4684, 4868, 1040SS, 1040PR, 1040X, 8888, or 8862
• You aren’t filing on behalf of a deceased taxpayer
• You must report income on a Form W-2, 1099-R, or Sched C
• You must open or have an existing Credit Karma MoneyTM checking account1.