TurboTax does not support IRS Form 5074.
You need to complete the Form 5074 outside of TurboTax following the instructions on the form and include the Form 5074 with your federal tax return. The federal tax return, Form 1040, will have to be printed and mailed as you cannot add the Form 5074 to an e-filed tax return. The mailing instructions for your personal tax return, Form 1040, are included in the Form 5074 instructions.
IRS Form 5074, Allocation of Individual Income Tax to Guam or the Commonwealth of the Northern Mariana Islands (CNMI) including instructions - https://www.irs.gov/pub/irs-pdf/f5074.pdf
See this TurboTax support FAQ for printing a tax return for mailing when using the online editions - https://ttlc.intuit.com/questions/1944348-how-do-i-print-and-mail-my-return-in-turbotax-online