Hello jenniefromlewes,
Thanks for using Apple Support Communities! It looks like you inadvertently created two users for yourself on your new Mac and I'd like to do what I can to help.
If you have a Time Machine backup of your Mac, you can follow the steps to restore files to the correct user:
Use Time Machine to restore deleted files or older files
Deleting a user instructions can be found here: Delete a user or group on Mac
If your email account is a POP account, which allows email to be downloaded to only one "device", in this case user accounts. If your email account is IMAP, then email should be downloading to both "devices". The Mail User Guide has a troubleshooting section which can help: Troubleshoot email problems in Mail on Mac
If you have any questions or need additional assistance, you'll want to contact Apple Support.
Take care!