You would have received an email invitation to NetSuite after completing all of your profile information. That link, however, is only good for 24 hours (because it is a secure link). If you need a new link to access your account for the first time, please email email@example.com.
If you are looking for the URL to be able to sign back into NetSuite, use this: NetSuite Login. You will be able to sign in with the credentials you entered at sign up.