If you didn't sell ALL the shares acquired by year end, then you do need to put that information into TurboTax.
Tell TurboTax about the shares unsold at year end using the "ISO Exercise & Hold" interview. TurboTax will make an adjusting entry for these unsold shares (# of shares unsold) x (per share "spread" between FMV and strike price) on Form 6251. That interview will ask for your Form 3921 information.
Tom Young
