I mistakenly entered several customer invoices with the wrong ID and generated the invoices. They have not bee sent out and none are paid.

Can anyone give me a step by step instruction on how to change the invoice Bill To - customer ID to the correct one. I am new to this job and can not afford to screw up the books and lose my job....please answer as soon as possible.  These are on a Peachtree Application that is no longer supported, as I understand.

HELP