You can't edit or correct the GEDCOM file you uploaded to WikiTree, but you can edit or correct the program or site from or at which you created your GEDCOM so that next time you use that program or site to produce a GEDCOM the corrections will be there.
By the way, a difference of 60 years on a death date is quite a lot. Are you absolutely sure they are the same person? Could be a typo, sure, but there are so many people with the same name that it is possible for the ones you're looking at to be totally different people. Be sure other data items matches before you definitely mark this as a match.