the explanation for what you did goes in 1040X Part III.
you can be as terse or prolific as you see fit.
meanwhile just prepare a correct tax return and collect the pages that changed for attachment to form 1040x.
The operative word is correct. You must be certain your revised return is correct before reviewing Form 1040X.
Note: if 8949 changes, then Schedule D will change also.
IMHO, the easiest path is to fill out 1040X by hand yourself, by eyeball comparison of the original and revised Form 1040 placed side-by-side.
