On Step 8 Finalizing, sub-step Payment you are able to view the total fee that needs to be covered for the use of the Sprintax services. For you to obtain your tax forms prepared by Sprintax, you have to click on 'Checkout'. You will have to option to either pay via a link or using your card.
If you have an access code, you can apply it on Step 8 Finalizing, sub-step Review by navigating towards the 'Access code' box:
After you enter your code, you'll have to click on the 'Validate' option. Once you successfully apply the code, you can proceed onto the next step.
Important: Please note that the Sprintax fee that you pay here is not affiliated with the amount that you may owe to the IRS/State Tax Office. Keep in mind that Sprintax only prepares the tax forms for you which you need to file to the relevant US tax authorities. Any potential tax refund or tax debt on your tax return has to be handled by you as you're the taxpayer.