Are you asking if you can file for another person using TurboTax Online? You can, but you'll need a separate account for the other person. And you'll be required to pay again for the second return. See the TurboTax FAQ below for instructions.
"How do I start another return in TurboTax Online?"
https://ttlc.intuit.com/replies/3288574
In the future, if you need to file more than one return (maybe for family members), you may want to consider using TurboTax Desktop (CD/Download) platform. Users can prepare unlimited returns and e-file up to 5 federal returns. See the TurboTax FAQ below for more information.
"What are the advantages of TurboTax CD/Download software over the Online version?"
https://ttlc.intuit.com/replies/4535178
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***