There may be an "upload new version link" in the Application and Admissions section. If so, your option is clear. All such changes have to be made prior to the deadline for admissions.
Notice at the link below the particular section on Applications and Admissions. A matter of updating a transcript or resume was offered. The above mentioned reply was offered. If this proves unavailable, I would correspond to the admissions address and probably attach the correction prior to the admissions deadline if it is impending. If not, I might query as to the method of correction.
It is possible that the FAQS page related to admissions in the program at the particular institution of interest may provide the information. --But I sense that all such pages will refer to "updating" rather than errors.