I shared a marketplace policy with more than one person. How do I enter that in TurboTax?

you first enter the 1095-A amounts

 

 

then there is a section to allocate amounts to other taxpayers.  Every column for any month must use the same % of the totals for that month allocated to others. You also need to provide others with the info so they can properly file their returns. 

 

 

you do not have to allocate to others unless the policy covers a person who is not a dependent on your return.