How are you interpreting the word "trustee"?
If you are representing individual taxpayers (including filing returns), refer to the link below.
If you mean how do you file as a Representative for other taxpayers:
You may be authorized to sign either as the taxpayer's representative or agent. Generally, a representative must be an individual eligible to practice before the IRS, such as an enrolled agent, attorney, or CPA; a family member (limited to spouse, parent, child, brother, or sister) may also act as your representative.
Click here for additional information on Form 2848, Power of Attorney.
Click here for additional information on Power of Attorney and other authorizations.
If you mean how do you file as a Trustee or file a return for a Trust:
You'll need TurboTax Business to file Form 1041, as the personal versions of TurboTax don't support this form.
TurboTax Business is available for Windows on CD or as a download. It's not available for Mac or in our online versions of TurboTax.
After you install TurboTax Business and begin working on your return, you'll be asked which type of return you need to prepare. Select Trust or Estate return (Form 1041) and proceed.
Click here for additional information on Estates and Trusts.
Click here for a video on filing a Fiduciary Tax Return.
If this does not help please feel free to come back to TurboTax Community additional questions or click here for information on Turbo Tax Support. You can connect with a Live TurboTax Agent and share your screen.