Am I able to use my turbotax account to do someones elses taxes?

The TurboTax online editions can only be used for one tax return per account and User ID.  If you want to start another tax return with the online editions you will need to create a new account with a new User ID.

Please read this TurboTax Help topic on how to start a new tax return for another person.

If you are using TurboTax Online, you cannot prepare and file a tax return for another person using an existing TurboTax account. You'll need to create a new account.

If you are using TurboTax Desktop, you can start a new return for yourself by clicking on Start a new return on the Welcome page of TurboTax.