I'm trying to install ebizmart to connect Mailchimp and magento but for some reason, when i paste in the extension code to install it said "it already existed". I went back again and do not see any new Mailchimp tab under Customer nor Mailchimp anywhere in Magento. However I do see a Mandrill account connected. How do I connect my MailChimp then?
Did you try clearing the Magento cache? It should've been done automatically but it won't hurt you to try it.
If that doesn't work you should try to uninstall and then install again. You will see the option to uninstall in the grid below at Magento Connect Manager.
Maybe the installation was not finished successfully the first time.
If you're seeing a Mandrill connection then you've at least partly installed it. Like Santiago suggested, it's a good idea to just uninstall whatever stage has been installed before and go again.