if the return is complete, pay whatever fees print it out, and mail it.
if not finished you'll need to buy the 2021 desktop app to complete and then mail it.
https://turbotax.intuit.com/personal-taxes/past-years-products/2021/
other sites might sell it for less but beware that some sites will sell you malware
the return can not be efiled
attach withholding forms
mail federal and state, if applicable, separately
use a method where you can either track it or get a notification of delivery.