DD214 is not a tax form and is not entered on the Federal tax return.
DD214 Report of Separation is generally issued when a service member performs active duty or at least 90 consecutive days of active duty training.
The Report of Separation contains information normally needed to verify military service for benefits, retirement, employment and membership in veterans' organizations. Information shown on the Report of Separation may include the service member's:
You don't file a DD214
However, if you left the service during 2021,
...and you get aW-2 form from the DOD/DFAS for the time you were in service during 2021.
1) On the My Info page, you edit yoru personal information, and indicate that you were Active duty during 2021....once you hit the Active Duty button, you will then get more selections...one to indicate that you left service during 2021.
2) When you do enter that military W-2 form, on a page after the main entries, there will be a page with a whole list of checkboxes....make sure you check the box indicating it was a W-2 for "Active Duty" in the military.
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Keep that DD214 carefully protected. IF you are returning to your hometown, some County Clerk offices will archive a certified copy of that DD214, so that if you ever lose yours, you can get a copy from them. Mine gave me a couple extra certified copies, and even a reduced pocket-sized copy with the county's raised seal impressed on it.