Log in to your account.
Click on "Find a Swimmer", search for the swimmer you want to edit and click on them.
At the top of the page click on "Edit Swimmer". You can now change the gender, name, and ID for the swimmer. If you edit the name or gender Swimgen will do its best to modify all existing report cards to use the swimmers new gender and name. You should double check to make sure you are happy with the report cards after renaming.