If I have 2 other people on my 1095-A how do I enter both under the shared policy when Turbo Tax seems to only allow one to be added for the allocation amounts?

You don't have to list both of the other people that you share the Marketplace policy with when your enter your shared policy.  Just include one person and make sure all of the percentages for  your premium, your SLCSP, and your advance payment adds up to 100% for everyone who shares the policy and enters it on their tax return 

The percentages that you should enter for your premium, your SLCSP, and your advance payment should be an amount that everyone agrees on. It could be 34/33/33, 100/0/0, 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.

Share this TurboTax article I'm on my parents' 1095-A form. What do I do on my return? with the people that you share the policy with so they can correctly enter their1095-A. (It applies even if the other people aren't your children.)

Review the example from the IRS website regarding Other Taxpayers Allocating Policy Amounts With Two or More Other Taxpayers for additional information (scroll down to the highlighted section).

To return to the Form 1095-A entry screen, refer to the TurboTax Help article Where do I enter my 1095-A?