Anyone with a valid email address can create a 23andMe account at any time. Note that although you enter an email address when placing an order in the 23andMe store, placing an order does not create an account.
Most customers will create their accounts as part of registration after they have received their kits in the mail. If you do not have an account or wish to register your kit into a new account under a new email address, go to https://www.23andme.com/user/claim/ to create a new account and register your kit:
Note that your account setup is not complete until you create a password and confirm your email address.