how to I add more people to my marketplace policy to allocate for policy amounts

For family members that you share a Marketplace Health Insurance policy with that aren't on your tax return, each of you will need to enter the 1095-A on your tax returns. TurboTax will ask you questions about if the policy was shared with someone and how to allocate the costs and credit. 

The percentages that you should enter for your premium, your SLCSP, and your advance payment should be an amount that you and the persons you share it with agree on. It could be 50/25/25 or another amount. Make sure you are in agreement and that the percentages on all tax returns add up to 100% together.

TurboTax will calculate the information that should be on your return based on your answers.

You can review this TurboTax article I'm on my parents' 1095-A form. What do I do on my return? for more information.